Merge remote-tracking branch 'upstream/master'

# Conflicts:
#	.travis.yml
#	DIRECTORY.md
#	README.md

872.c

@@ -0,0 +1,43 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     struct TreeNode *left;
+ *     struct TreeNode *right;
+ * };
+ */
+
+
+bool leafSimilar(struct TreeNode* root1, struct TreeNode* root2){
+    int sequence1[100] ={0}, sequence2[100]={0}, num_of_node1 =0,num_of_node2 =0;
+    
+    num_of_node1 = sequence(root1,sequence1,num_of_node1);
+    num_of_node2 = sequence(root2,sequence2,num_of_node2);
+
+    if (num_of_node1 != num_of_node2)
+        return false;
+       
+    for (int i = 0;i<num_of_node1; i++){
+        if (sequence1[i] != sequence2[i])
+            return false;
+    }
+    return true;
+}
+
+
+int sequence(struct TreeNode* root ,int *list , int num_of_node){
+
+    if (!root)
+        return num_of_node;
+    
+    if (!root->left &&  !root->right){
+        list[num_of_node] = root->val;
+        num_of_node ++;
+        return num_of_node;
+    }
+    
+    num_of_node = sequence(root->left ,list , num_of_node);
+    num_of_node = sequence(root->right ,list , num_of_node);
+    
+    return num_of_node; 
+}

README.md

@@ -1,6 +1,5 @@
 [![Build Status](https://travis-ci.org/kvedala/C.svg?branch=master)](https://travis-ci.org/kvedala/C)
 C
-========
 
 For a full list of all algorithms, please see: [DIRECTORY.md](https://github.com/TheAlgorithms/C/blob/master/DIRECTORY.md)
 
@@ -41,6 +40,9 @@ All the code can be executed and tested online: [![using Google Colab Notebook](
 		- recursive_traversals
 	- trie
 		- trie
+	- heap
+		- min heap
+		- max heap 
 
 
 ## Searching

conversions/octal_to_decimal.c

@@ -0,0 +1,38 @@
+#include <math.h>
+#include <stdio.h>
+
+// Converts octal number to decimal
+int convertValue(int num, int i) {
+    return num * pow(8, i);
+}
+
+long long toDecimal(int octal_value) {
+
+    int decimal_value = 0, i = 0;
+
+    while (octal_value) {
+
+        // Extracts right-most digit and then multiplies by 8^i
+        decimal_value += convertValue(octal_value % 10, i++);
+
+        // Shift right in base 10
+        octal_value /= 10;
+    }
+
+    return decimal_value;
+}
+
+int main() {
+
+    printf("Enter octal value: ");
+
+    int octal_value;
+
+    scanf("%d", &octal_value);
+
+    long long result = toDecimal(octal_value);
+
+    printf("%d in decimal is %lld\n", octal_value, result);
+
+    return 0;
+}

data_structures/Array/README.md

@@ -2,6 +2,10 @@
 
 Simple array of integers. With I/O functions, Sort Functions and Search Functions.
 
+#Sort Function
+
+The Sort function sorts the elements in the range in a particular order. The different types of sorting methods are Bubble Sort, Selection Sort, Merge Sort and Quick Sort. Bubble Sort repeatedly sorts the adjacent elements if they are in wrong order.
+
 ## Structure
 
 ```C

data_structures/graphs/Graph.c

@@ -0,0 +1,102 @@
+// Graph ADT
+// Adjacency Matrix Representation  
+#include "Graph.h"
+#include <assert.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+typedef struct GraphRep {
+   int  **edges;   // adjacency matrix
+   int    nV;      // #vertices
+   int    nE;      // #edges
+} GraphRep;
+
+Graph newGraph(int V) {
+   assert(V >= 0);
+   int i;
+
+   Graph g = malloc(sizeof(GraphRep));
+   assert(g != NULL);
+   g->nV = V;
+   g->nE = 0;
+
+   // allocate memory for each row
+   g->edges = malloc(V * sizeof(int *));
+   assert(g->edges != NULL);
+   // allocate memory for each column and initialise with 0
+   for (i = 0; i < V; i++) {
+      g->edges[i] = calloc(V, sizeof(int));
+      assert(g->edges[i] != NULL);
+   }
+
+   return g;
+}
+
+// check if vertex is valid in a graph
+bool validV(Graph g, Vertex v) {
+   return (g != NULL && v >= 0 && v < g->nV);
+}
+
+void insertEdge(Graph g, Edge e) {
+   assert(g != NULL && validV(g,e.v) && validV(g,e.w));
+
+   if (!g->edges[e.v][e.w]) {  // edge e not in graph
+      g->edges[e.v][e.w] = 1;
+      g->edges[e.w][e.v] = 1;
+      g->nE++;
+   }
+}
+
+void removeEdge(Graph g, Edge e) {
+   assert(g != NULL && validV(g,e.v) && validV(g,e.w));
+
+   if (g->edges[e.v][e.w]) {   // edge e in graph
+      g->edges[e.v][e.w] = 0;
+      g->edges[e.w][e.v] = 0;
+      g->nE--;
+   }
+}
+
+bool adjacent(Graph g, Vertex v, Vertex w) {
+   assert(g != NULL && validV(g,v) && validV(g,w));
+
+   return (g->edges[v][w] != 0);
+}
+
+void showGraph(Graph g) {
+    assert(g != NULL);
+    int i, j;
+
+    printf("Number of vertices: %d\n", g->nV);
+    printf("Number of edges: %d\n", g->nE);
+    for (i = 0; i < g->nV; i++)
+       for (j = i+1; j < g->nV; j++)
+	  if (g->edges[i][j])
+	      printf("Edge %d - %d\n", i, j);
+}
+
+void freeGraph(Graph g) {
+   assert(g != NULL);
+
+   int i;
+   for (i = 0; i < g->nV; i++)
+      free(g->edges[i]);
+   free(g->edges);
+   free(g);
+}
+
+// By 
+//  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+// | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+// | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+// | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+// | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+// | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+// | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+// | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+// | |              | || |              | || |              | || |              | | | |              | || |              | |
+// | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+//  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+//  Email :    z5261243@unsw.edu.au
+//             hhoanhtuann@gmail.com

data_structures/graphs/Graph.h

@@ -0,0 +1,37 @@
+// Graph ADT interface ... COMP2521 
+#include <stdbool.h>
+
+typedef struct GraphRep *Graph;
+
+// vertices are ints
+typedef int Vertex;
+
+// edges are pairs of vertices (end-points)
+typedef struct Edge {
+   Vertex v;
+   Vertex w;
+} Edge;
+
+Graph newGraph(int);
+void  insertEdge(Graph, Edge);
+void  removeEdge(Graph, Edge);
+bool  adjacent(Graph, Vertex, Vertex);
+void  showGraph(Graph);
+void  freeGraph(Graph);
+
+
+// By 
+//  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+// | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+// | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+// | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+// | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+// | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+// | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+// | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+// | |              | || |              | || |              | || |              | | | |              | || |              | |
+// | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+//  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+//  Email :    z5261243@unsw.edu.au
+//             hhoanhtuann@gmail.com

data_structures/graphs/Makefile

@@ -0,0 +1,56 @@
+CC=gcc 
+CFLAGS=-Wall -Werror -std=c99
+all: BFS Bellman-Ford DFS Dijkstra Floyd-Warshall bfsQueue dfsRecursive euler hamiltonian strongly_connected_components topologicalSort transitiveClosure
+
+
+BFS: BFS.c
+	$(CC) -o BFS BFS.c
+Bellman-Ford: Bellman-Ford.c
+	$(CC) -o Bellman-Ford Bellman-Ford.c
+DFS: DFS.c
+	$(CC) -o DFS DFS.c
+Dijkstra: Dijkstra.c
+	$(CC) -o Dijkstra Dijkstra.c
+Floyd-Warshall: Floyd-Warshall.c
+	$(CC) -o Floyd-Warshall Floyd-Warshall.c
+Graph.o: Graph.c Graph.h
+	$(CC) $(CFLAGS) -c Graph.c
+bfsQueue: Graph.o queue.o bfsQueue.o
+	$(CC) Graph.o queue.o bfsQueue.o -o bfsQueue
+bfsQueue.o: bfsQueue.c
+	$(CC) $(CFLAGS) -c bfsQueue.c
+dfsRecursive: Graph.o queue.o dfsRecursive.o
+	$(CC) Graph.o queue.o dfsRecursive.o -o dfsRecursive
+dfsRecursive.o: dfsRecursive.c
+	$(CC) -c dfsRecursive.c
+euler: Graph.o euler.o
+	$(CC) Graph.o euler.o -o euler
+euler.o: euler.c
+	$(CC) $(CFLAGS) -c euler.c
+hamiltonian: Graph.o hamiltonian.o
+	$(CC) Graph.o hamiltonian.o -o hamiltonian
+hamiltonian.o: hamiltonian.c
+	$(CC) $(CFLAGS) -c hamiltonian.c
+queue.o: queue.c queue.h
+	$(CC) $(CFLAGS) -c queue.c
+strongly_connected_components: strongly_connected_components.c
+	$(CC) -o strongly_connected_components strongly_connected_components.c
+topologicalSort: topologicalSort.c
+	$(CC) -o topologicalSort topologicalSort.c
+transitiveClosure: transitiveClosure.c
+	$(CC) -o transitiveClosure transitiveClosure.c
+# By 
+#  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+# | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+# | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+# | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+# | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+# | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+# | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+# | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+# | |              | || |              | || |              | || |              | | | |              | || |              | |
+# | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+#  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+#  Email :    z5261243@unsw.edu.au
+#             hhoanhtuann@gmail.com

data_structures/graphs/bfsQueue.c

@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include "queue.h"
+#include "Graph.h"
+
+#define MAX_NODES 1000
+
+int visited[MAX_NODES];  // array to store visiting order
+                         // indexed by vertex 0..nV-1
+
+bool findPathBFS(Graph g, int nV, Vertex src, Vertex dest) {
+   Vertex v;
+   for (v = 0; v < nV; v++)
+      visited[v] = -1;
+
+   visited[src] = src;
+   queue Q = newQueue();
+   QueueEnqueue(Q, src);
+   while (!QueueIsEmpty(Q)) {
+      v = QueueDequeue(Q);
+      Vertex w;
+      for (w = 0; w < nV; w++)
+      if (adjacent(g, v, w) && visited[w] == -1) {
+         visited[w] = v;
+         if (w == dest)
+            return true;
+         else
+            QueueEnqueue(Q, w);
+      }
+   }
+   return false;
+}
+
+int main(void) {
+   int V = 10;
+   Graph g = newGraph(V);
+
+   Edge e;
+   e.v = 0; e.w = 1; insertEdge(g, e);
+   e.v = 0; e.w = 2; insertEdge(g, e);
+   e.v = 0; e.w = 5; insertEdge(g, e);
+   e.v = 1; e.w = 5; insertEdge(g, e);
+   e.v = 2; e.w = 3; insertEdge(g, e);
+   e.v = 3; e.w = 4; insertEdge(g, e);
+   e.v = 3; e.w = 5; insertEdge(g, e);
+   e.v = 3; e.w = 8; insertEdge(g, e);
+   e.v = 4; e.w = 5; insertEdge(g, e);
+   e.v = 4; e.w = 7; insertEdge(g, e);
+   e.v = 4; e.w = 8; insertEdge(g, e);
+   e.v = 5; e.w = 6; insertEdge(g, e);
+   e.v = 7; e.w = 8; insertEdge(g, e);
+   e.v = 7; e.w = 9; insertEdge(g, e);
+   e.v = 8; e.w = 9; insertEdge(g, e);
+
+   int src = 0, dest = 6;
+   if (findPathBFS(g, V, src, dest)) {
+      Vertex v = dest;
+      while (v != src) {
+	 printf("%d - ", v);
+	 v = visited[v];
+      }
+      printf("%d\n", src);
+   }
+   return 0;
+}
+
+// By 
+//  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+// | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+// | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+// | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+// | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+// | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+// | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+// | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+// | |              | || |              | || |              | || |              | | | |              | || |              | |
+// | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+//  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+//  Email :    z5261243@unsw.edu.au
+//             hhoanhtuann@gmail.com

data_structures/graphs/dfsRecursive.c

@@ -0,0 +1,74 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include "Graph.h"
+
+#define MAX_NODES 1000
+
+int visited[MAX_NODES];  // array to store visiting order
+                         // indexed by vertex 0..nV-1
+
+bool dfsPathCheck(Graph g, int nV, Vertex v, Vertex dest) {
+   Vertex w;
+   for (w = 0; w < nV; w++)
+      if (adjacent(g, v, w) && visited[w] == -1) {
+         visited[w] = v;
+         if (w == dest)
+	    return true;
+         else if (dfsPathCheck(g, nV, w, dest))
+            return true;
+      }
+   return false;
+}
+
+bool findPathDFS(Graph g, int nV, Vertex src, Vertex dest) {
+   Vertex v;
+   for (v = 0; v < nV; v++)
+      visited[v] = -1;
+   visited[src] = src;
+   return dfsPathCheck(g, nV, src, dest);
+}
+
+int main(void) {
+   int V = 6;
+   Graph g = newGraph(V);
+
+   Edge e;
+   e.v = 0; e.w = 1; insertEdge(g, e);
+   e.v = 0; e.w = 4; insertEdge(g, e);
+   e.v = 0; e.w = 5; insertEdge(g, e);
+   e.v = 5; e.w = 4; insertEdge(g, e);
+   e.v = 4; e.w = 2; insertEdge(g, e);
+   e.v = 4; e.w = 3; insertEdge(g, e);
+   e.v = 5; e.w = 3; insertEdge(g, e);
+   e.v = 1; e.w = 2; insertEdge(g, e);
+   e.v = 3; e.w = 2; insertEdge(g, e);
+
+   int src = 0, dest = 5;
+   if (findPathDFS(g, V, src, dest)) {
+      Vertex v = dest;
+      while (v != src) {
+	 printf("%d - ", v);
+	 v = visited[v];
+      }
+      printf("%d\n", src);
+   }
+   return 0;
+}
+
+
+// By 
+//  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+// | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+// | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+// | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+// | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+// | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+// | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+// | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+// | |              | || |              | || |              | || |              | | | |              | || |              | |
+// | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+//  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+//  Email :    z5261243@unsw.edu.au
+//             hhoanhtuann@gmail.com
+

data_structures/graphs/euler.c

@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include "Graph.h"
+
+// Return the number of vertices that v is 
+// connected to
+int degree(Graph g, int nV, Vertex v) {
+   int deg = 0;
+   Vertex w;
+   for (w = 0; w < nV; w++)
+      if (adjacent(g, v, w))
+	 deg++;
+   return deg;
+}
+
+// If start from vertex v, decide if the 
+// graph has euler path
+bool hasEulerPath(Graph g, int nV, Vertex v, Vertex w) {
+   if (v != w) {
+      if (degree(g, nV, v) % 2 == 0 || degree(g, nV, w) % 2 == 0)
+	      return false;
+   } else if (degree(g, nV, v) % 2 != 0) {
+      return false;
+   }
+   Vertex x;
+   for (x = 0; x < nV; x++)
+      if (x != v && x != w && degree(g, nV, x) % 2 != 0)
+	 return false;
+   return true;
+}
+
+int main(void) {
+   Edge e;
+   int n;
+
+   printf("Enter the number of vertices: ");
+   scanf("%d", &n);
+   Graph g = newGraph(n);
+
+   Vertex src, dest;
+   printf("Enter source node: ");
+   scanf("%d", &src);
+   printf("Enter destination node: ");
+   scanf("%d", &dest);
+   
+   printf("Enter an edge (from): ");
+   while (scanf("%d", &e.v) == 1) {
+      printf("Enter an edge (to): ");
+      scanf("%d", &e.w);
+      insertEdge(g, e);
+      printf("Enter an edge (from): ");
+   }
+   printf("Finished.\n");
+
+   printf("The graph has ");
+   if (hasEulerPath(g, n, src, dest))
+      printf("an");
+   else
+      printf("no");
+   printf(" Euler path from %d to %d.\n", src, dest);
+
+   freeGraph(g);
+   return 0;
+}
+
+
+
+// By 
+//  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+// | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+// | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+// | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+// | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+// | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+// | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+// | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+// | |              | || |              | || |              | || |              | | | |              | || |              | |
+// | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+//  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+//  Email :    z5261243@unsw.edu.au
+//             hhoanhtuann@gmail.com

data_structures/graphs/hamiltonian.c

@@ -0,0 +1,87 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include "Graph.h"
+
+#define MAX_NODES 1000
+
+bool visited[MAX_NODES];
+
+bool hamiltonR(Graph g, int nV, Vertex v, Vertex dest, int d) {
+// v = current vertex considered
+// dest = destination vertex
+// d = distance "remaining" until path found
+
+   Vertex w;
+   if (v == dest) {
+      return (d == 0);
+   } else {
+      visited[v] = true;
+      for (w = 0; w < nV; w++) {
+	 if (adjacent(g, v, w) && !visited[w]) {
+	    if (hamiltonR(g, nV, w, dest, d-1)) {
+	       return true;
+	    }
+	 }
+      }
+   }
+   visited[v] = false;
+   return false;
+}
+
+bool hasHamiltonianPath(Graph g, int nV, Vertex src, Vertex dest) {
+   Vertex v;
+   for (v = 0; v < nV; v++)
+      visited[v] = false;
+   return hamiltonR(g, nV, src, dest, nV-1);
+}
+
+int main(void) {
+   Edge e;
+   int n;
+
+   printf("Enter the number of vertices: ");
+   scanf("%d", &n);
+   Graph g = newGraph(n);
+
+   Vertex src, dest;
+   printf("Enter source node: ");
+   scanf("%d", &src);
+   printf("Enter destination node: ");
+   scanf("%d", &dest);
+   
+   printf("Enter an edge (from): ");
+   while (scanf("%d", &e.v) == 1) {
+      printf("Enter an edge (to): ");
+      scanf("%d", &e.w);
+      insertEdge(g, e);
+      printf("Enter an edge (from): ");
+   }
+   printf("Finished.\n");
+
+   printf("The graph has ");
+   if (hasHamiltonianPath(g, n, src, dest))
+      printf("a");
+   else
+      printf("no");
+   printf(" Hamiltonian path from %d to %d.\n", src, dest);
+
+   freeGraph(g);
+   return 0;
+}
+
+
+// By 
+//  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+// | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+// | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+// | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+// | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+// | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+// | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+// | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+// | |              | || |              | || |              | || |              | | | |              | || |              | |
+// | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+//  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+//  Email :    z5261243@unsw.edu.au
+//             hhoanhtuann@gmail.com

data_structures/graphs/kruskal.c

@@ -27,7 +27,7 @@ struct Graph
 // Creates a graph with V vertices and E edges 
 struct Graph* createGraph(int V, int E) 
 { 
-	struct Graph* graph = new Graph; 
+	struct Graph* graph = new Graph(); 
 	graph->V = V; 
 	graph->E = E; 
 

data_structures/graphs/queue.c

@@ -0,0 +1,88 @@
+// Queue ADT implementation ... COMP2521 
+
+#include <stdlib.h>
+#include <assert.h>
+#include "queue.h"
+
+typedef struct node {
+   int data;
+   struct node *next;
+} NodeT;
+
+typedef struct QueueRep {
+   int   length;
+   NodeT *head;
+   NodeT *tail;
+} QueueRep;
+
+// set up empty queue
+queue newQueue() {
+   queue Q = malloc(sizeof(QueueRep));
+   Q->length = 0;
+   Q->head = NULL;
+   Q->tail = NULL;
+   return Q;
+}
+
+// remove unwanted queue
+void dropQueue(queue Q) {
+   NodeT *curr = Q->head;
+   while (curr != NULL) {
+      NodeT *temp = curr->next;
+      free(curr);
+      curr = temp;
+   }
+   free(Q);
+}
+
+// check whether queue is empty
+int QueueIsEmpty(queue Q) {
+   return (Q->length == 0);
+}
+
+// insert an int at end of queue
+void QueueEnqueue(queue Q, int v) {
+   NodeT *new = malloc(sizeof(NodeT));
+   assert(new != NULL);
+   new->data = v;
+   new->next = NULL;
+   if (Q->tail != NULL) {
+      Q->tail->next = new;
+      Q->tail = new;
+   } else {
+      Q->head = new;
+      Q->tail = new;
+   }
+   Q->length++;
+}
+
+// remove int from front of queue
+int QueueDequeue(queue Q) {
+   assert(Q->length > 0);
+   NodeT *p = Q->head;
+   Q->head = Q->head->next;
+   if (Q->head == NULL) {
+      Q->tail = NULL;
+   }
+   Q->length--;
+   int d = p->data;
+   free(p);
+   return d;
+}
+
+
+// By 
+//  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+// | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+// | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+// | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+// | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+// | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+// | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+// | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+// | |              | || |              | || |              | || |              | | | |              | || |              | |
+// | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+//  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+//  Email :    z5261243@unsw.edu.au
+//             hhoanhtuann@gmail.com

data_structures/graphs/queue.h

@@ -0,0 +1,26 @@
+// Queue ADT header file ... COMP2521 
+
+typedef struct QueueRep *queue;
+
+queue newQueue();               // set up empty queue
+void  dropQueue(queue);         // remove unwanted queue
+int   QueueIsEmpty(queue);      // check whether queue is empty
+void  QueueEnqueue(queue, int); // insert an int at end of queue
+int   QueueDequeue(queue);      // remove int from front of queue
+
+
+// By 
+//  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+// | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+// | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+// | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+// | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+// | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+// | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+// | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+// | |              | || |              | || |              | || |              | | | |              | || |              | |
+// | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+//  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+//  Email :    z5261243@unsw.edu.au
+//             hhoanhtuann@gmail.com

data_structures/graphs/strongly_connected_components.c

@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #define MAX_SIZE 40//Assume 40 nodes at max in graph
+#define INT_MIN  0
 //A vertex of the graph 
 struct node
 {
@@ -195,6 +196,7 @@ struct Stack* createStack()
 {
 	struct Stack* stack=malloc(sizeof(struct Stack));
 	stack->top=-1;
+    return stack;
 }
 //Pushes element into stack
 void push(struct Stack* stack,int element)

data_structures/graphs/topologicalSort.c

@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #define MAX_SIZE 40//Assume 40 nodes at max in graph
+#define INT_MIN  0
 //A vertex of the graph 
 struct node
 {
@@ -147,6 +148,7 @@ struct Stack* createStack()
 {
 	struct Stack* stack=malloc(sizeof(struct Stack));
 	stack->top=-1;
+    return stack;
 }
 //Pushes element into stack
 void push(struct Stack* stack,int element)

data_structures/graphs/transitiveClosure.c

@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <stdbool.h>
+
+#define NODES 4
+
+int digraph[NODES][NODES]={ {0,1,1,1}, {1,0,1,0}, {0,1,0,0}, {0,0,0,0} };
+int tc[NODES][NODES];
+
+void warshall() {
+   int i, s, t;
+   for (s = 0; s < NODES; s++)
+      for (t = 0; t < NODES; t++)
+	 tc[s][t] = digraph[s][t];
+
+   for (i = 0; i < NODES; i++)
+      for (s = 0; s < NODES; s++)
+	 for (t = 0; t < NODES; t++)
+	    if (tc[s][i] && tc[i][t])
+	       tc[s][t] = 1;
+}
+
+int main(void) {
+   warshall();
+   int i, j;
+   for (i = 0; i < NODES; i++) {
+      for (j = 0; j < NODES; j++) {
+	 printf("%d ", tc[i][j]);
+      }
+      putchar('\n');
+   }
+   return 0;
+}
+
+// By 
+//  .----------------.  .----------------.  .----------------.  .-----------------.  .----------------.  .----------------. 
+// | .--------------. || .--------------. || .--------------. || .--------------. | | .--------------. || .--------------. |
+// | |  _________   | || | _____  _____ | || |      __      | || | ____  _____  | | | |  ____  ____  | || |     ____     | |
+// | | |  _   _  |  | || ||_   _||_   _|| || |     /  \     | || ||_   \|_   _| | | | | |_   ||   _| | || |   .'    `.   | |
+// | | |_/ | | \_|  | || |  | |    | |  | || |    / /\ \    | || |  |   \ | |   | | | |   | |__| |   | || |  /  .--.  \  | |
+// | |     | |      | || |  | '    ' |  | || |   / ____ \   | || |  | |\ \| |   | | | |   |  __  |   | || |  | |    | |  | |
+// | |    _| |_     | || |   \ `--' /   | || | _/ /    \ \_ | || | _| |_\   |_  | | | |  _| |  | |_  | || |  \  `--'  /  | |
+// | |   |_____|    | || |    `.__.'    | || ||____|  |____|| || ||_____|\____| | | | | |____||____| | || |   `.____.'   | |
+// | |              | || |              | || |              | || |              | | | |              | || |              | |
+// | '--------------' || '--------------' || '--------------' || '--------------' | | '--------------' || '--------------' |
+//  '----------------'  '----------------'  '----------------'  '----------------'   '----------------'  '----------------' 
+ 
+//  Email :    z5261243@unsw.edu.au
+//             hhoanhtuann@gmail.com

data_structures/hash_set/Makefile

@@ -0,0 +1,13 @@
+CC = gcc
+CFLAGS = -g -Wall
+
+all: main
+
+main: main.o hash_set.o
+	$(CC) $(CFLAGS) $^ -o $@
+
+hash_set.o: hash_set.c
+	$(CC) $(CFLAGS) -c $^
+
+clean:
+	rm *.o main

data_structures/hash_set/hash_set.c

@@ -0,0 +1,92 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "hash_set.h"
+
+extern hash_set_t *init_hash_set()
+{
+    hash_set_t *set = (hash_set_t *)malloc(sizeof(hash_set_t));
+    set->keys = calloc(DEFAULT_HASH_SET_CAPACITY, sizeof(void **));
+    set->values = calloc(DEFAULT_HASH_SET_CAPACITY, sizeof(void **));
+    set->length = 0;
+    set->capacity = DEFAULT_HASH_SET_CAPACITY;
+
+    return set;
+}
+
+unsigned add(hash_set_t *set, void *value)
+{
+    return put(set, hash(value), value);
+}
+
+unsigned put(hash_set_t *set, long long hash, void *value)
+{
+    if (contains_hash(set, hash)) {
+        if (set->keys[retrieve_index_from_hash(hash, set->capacity)] == value) {
+            return 0;
+        }
+
+        // collision
+        resize(set);
+
+        return put(set, hash, value);
+    }
+
+    set->keys[retrieve_index_from_hash(hash, set->capacity)] = value;
+    set->values[set->length++] = value;
+
+    return 1;
+}
+
+int contains(hash_set_t *set, void *value)
+{
+    return set->keys[retrieve_index_from_hash(hash(value), set->capacity)] == value ? 1 : 0;
+}
+
+int contains_hash(hash_set_t *set, long long hash)
+{
+    return set->keys[retrieve_index_from_hash(hash, set->capacity)] ? 1 : 0;
+}
+
+void delete(hash_set_t *set, void *value) {
+    set->keys[retrieve_index_from_hash(hash(value), set->capacity)] = NULL;
+}
+
+
+// adler_32 hash
+long long hash(void *value)
+{
+    char *str = value;
+
+    int a = 1;
+    int b = 0;
+    const int MODADLER = 65521;
+
+    for (int i = 0; str[i] != '\0'; i++) {
+        a = (a + str[i]) % MODADLER;
+        b = (b + a) % MODADLER;
+    }
+
+    return (b << 16) | a;
+}
+
+unsigned retrieve_index_from_hash(const long long hash, const unsigned capacity)
+{
+    return (capacity - 1) & (hash ^ (hash >> 12));
+}
+
+void resize(hash_set_t *set)
+{
+    void **keys_resized = calloc((set->capacity <<= 1), sizeof(void **));
+
+    for (int i = 0; i < set->length; i++) {
+        keys_resized[retrieve_index_from_hash(hash(set->values[i]), set->capacity)] = set->values[i];
+    }
+
+    free(set->keys);
+
+    set->keys = keys_resized;
+
+    void **new_values = (void **)realloc(set->values, set->capacity * sizeof(void **));
+    set->values = new_values;
+}

data_structures/hash_set/hash_set.h

@@ -0,0 +1,31 @@
+#ifndef __HASH_SET__
+#define __HASH_SET__
+
+#define DEFAULT_HASH_SET_CAPACITY 1 << 10
+
+typedef struct {
+    unsigned capacity;
+    unsigned length;
+    void **values;
+    void **keys;
+} hash_set_t;
+
+extern hash_set_t *init_hash_set();
+
+extern unsigned add(hash_set_t *set, void *value);
+
+unsigned put(hash_set_t *set, long long hash, void *value);
+
+extern int contains(hash_set_t *set, void *value);
+
+int contains_hash(hash_set_t *set, long long hash);
+
+extern void delete(hash_set_t *set, void *value);
+
+extern long long hash(void *value);
+
+extern unsigned retrieve_index_from_hash(const long long hash, const unsigned capacity);
+
+extern void resize(hash_set_t *set);
+
+#endif

data_structures/hash_set/main.c

@@ -0,0 +1,42 @@
+#include <stdio.h>
+
+#include "hash_set.h"
+
+int main()
+{
+    hash_set_t *set = init_hash_set();
+
+    int v1 = 10, v2 = 20, v3 = 30, v4 = 40, v5 = 50, v6 = 60, v7 = 70;
+
+    printf("Value %d was add ? %d\n", v1, add(set, &v1));
+    printf("Value %d was add ? %d\n", v1, add(set, &v1));
+    printf("contains %d ? %d\n", v1, contains(set, &v1));
+
+    printf("Value %d was add ? %d\n", v2, add(set, &v2));
+    printf("Value %d was add ? %d\n", v2, add(set, &v2));
+    printf("contains %d ? %d\n", v2, contains(set, &v2));
+
+    printf("Value %d was add ? %d\n", v3, add(set, &v3));
+    printf("Value %d is add ? %d\n", v3, add(set, &v3));
+    printf("contains %d ? %d\n", v3, contains(set, &v3));
+
+    printf("Value %d was add ? %d\n", v4, add(set, &v4));
+    printf("Value %d was add ? %d\n", v4, add(set, &v4));
+    printf("contains %d ? %d\n", v4, contains(set, &v4));
+
+    printf("Value %d was add ? %d\n", v5, add(set, &v5));
+    printf("Value %d was add ? %d\n", v5, add(set, &v5));
+    printf("contains %d ? %d\n", v5, contains(set, &v5));
+
+    printf("Value %d is add ? %d\n", v6, add(set, &v6));
+    printf("Value %d is add ? %d\n", v6, add(set, &v6));
+    printf("contains %d ? %d\n", v6, contains(set, &v6));
+
+    printf("contains %d ? %d\n", v7, contains(set, &v7));
+
+    delete(set, &v6);
+
+    printf("contains %d ? %d\n", v6, contains(set, &v6));
+
+    return 0;
+}

data_structures/linked_list/CircularLinkedList.C

@@ -0,0 +1,155 @@
+/* Circularly Linked List (Basic Operations) - Program to create a Circularly linked list abstract data type and perform various operations on it (Variable first and last declared globally) */
+
+#include  <stdio.h>
+#include <conio.h>
+#include  <stdlib.h>
+#define  NULL  0
+
+/* Assume that the data portion of each node consists of ONLY an integer.*/
+struct  node
+{
+  int  data ;
+  struct  node  *next ;
+} ;
+
+struct  node  *first=NULL ;
+struct  node  *last=NULL ;
+/* first and last are global variables and need not be passed to any function. Any changes made to variables first and last by any of the functions in the program will be reflected in the entire program */
+
+/* This function is responsible for creating the Circularly Linked List right from the BEGINING. */
+void  create()
+{
+  int  i , n ;
+  struct  node  *pnode , *p ;
+
+  printf("Enter the number of nodes required:\n") ;
+  scanf("%d",&n) ;
+
+  printf("Enter the data value of each node:\n") ;
+  for(i=1 ; i<=n ; i++)
+  {
+    pnode=(struct node*)malloc(sizeof(struct node)) ;
+    if(pnode==NULL)
+    {
+      printf("Memory overflow. Unable to create.\n") ;
+      return ;
+    }
+
+    scanf("%d",&pnode->data) ;
+
+    if(first==NULL)
+	 first=last=pnode ;
+    else
+    {
+	  last->next=pnode ;
+	  last=pnode ;    /* last keeps track of last node */
+    }
+
+    last->next=first ;
+  }
+}
+
+/* This function will delete a node with value k from the Linked List if such a node exists */
+void  deletenode(int  k)
+{
+  struct  node  *p , *follow ;
+
+  /* searching the required node */
+  p=first ;
+  follow=NULL ;
+  while(follow!=last)
+  {
+    if(p->data==k)
+	  break ;
+    follow=p ;
+    p=p->next ;
+  }
+
+  if(follow==last)
+    printf("Required node not found.\n") ;
+  else
+  {
+    if(p==first&&p==last)  /* deleting the one and the only node */
+	  first=last=NULL ;
+    else if(p==first)       /* deleting the first node */
+    {
+      first=first->next ;
+      last->next=first ;
+    }
+    else if(p==last)      /* deleting the last node */
+    {
+      last=follow ;
+      last->next=first ;
+    }
+    else		/* deleting any other node */
+      follow->next=p->next ;
+
+    free(p) ;
+  }
+}
+
+/* This function will go through all the nodes of Linked List exactly once and will display data value of each node */
+void  traverse()
+{
+  struct  node  *p , *follow ;
+  if(first==NULL)
+    printf("Circularly Linked List Empty") ;
+  else
+  {
+    printf("Circularly Linked List is as shown: \n") ;
+
+    p=first ;
+    follow = NULL ;
+    while(follow!=last)
+    {
+      printf("%d " , p->data) ;
+      follow=p ;
+      p=p->next ;
+    }
+
+    printf("\n") ;
+  }
+}
+
+void main()
+{
+  int  x , k , ch ;
+  clrscr() ;
+  do
+  {
+    printf("\n Menu: \n") ;
+    printf("1:Create Linked List \n") ;
+    printf("2:Delete Node \n") ;
+    printf("3:Traverse \n") ;
+    printf("4:Exit \n") ;
+
+    printf("\nEnter your choice: ") ;
+    scanf("%d",&ch) ;
+
+    switch(ch)
+    {
+      case 1:
+      create() ;
+      break ;
+
+      case 2:
+      printf("Enter the data value of the node to be deleted: ") ;
+      scanf("%d",&k) ;
+      deletenode(k) ;
+      break ;
+
+      case 3:
+      traverse() ;
+      break ;
+
+      case 4:
+      break ;
+    }
+ }
+ while(ch!=4) ;
+
+ getch() ;
+}
+
+
+

data_structures/linked_list/singly_link_list_deletion.c

@@ -35,7 +35,7 @@ void insert()//function to insert at first location
   }
 }
 ///////////////////////////////////////////////////////////
-void deleteion()//function to delete from first position
+void deletion()//function to delete from first position
 {
     struct node *t;
     if(start==NULL)
@@ -85,7 +85,7 @@ int main()
             insert();
             break;
         case 2:
-            deleteion();
+            deletion();
             break;
         case 3:
             viewlist();

greedy_approach/djikstra.c

@@ -0,0 +1,79 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAX 20
+#define INF 999
+
+int mat[MAX][MAX];
+int V;
+
+int dist[MAX];
+
+int q[MAX];
+int qp = 0;
+
+void enqueue (int v) {
+	q[qp++] = v;
+}
+
+int cf (void *a, void *b) {
+	int *x = (int *)a;
+	int *y = (int *)b;
+	return *y - *x;
+}
+
+int dequeue () {
+	qsort(q, qp, sizeof(int), cf);
+	return q[--qp];
+}
+
+int queue_has_something () {
+	return (qp > 0);
+}
+
+int visited[MAX];
+int vp = 0;
+
+void dijkstra (int s) {
+	dist[s] = 0;
+	int i;
+	for (i = 0; i < V; ++i) {
+		if (i != s) {
+			dist[i] = INF;
+		}
+		enqueue(i);
+	}
+	while (queue_has_something()) {
+		int u = dequeue();
+		visited[vp++] = u;
+		for (i = 0; i < V; ++i) {
+			if (mat[u][i]) {
+				if (dist[i] > dist[u] + mat[u][i]) {
+					dist[i] = dist[u] + mat[u][i];
+				}
+			}
+		}
+	}
+}
+
+int main(int argc, char const *argv[]) {
+
+	printf("Enter the number of vertices: ");
+	scanf(" %d", &V);
+	printf("Enter the adj matrix: ");
+	int i, j;
+	for (i = 0; i < V; ++i) {
+		for (j = 0; j < V; ++j) {
+			scanf(" %d", &mat[i][j]);
+		}
+	}
+	
+	dijkstra(0);
+
+	printf("\nNode\tDist\n");
+	for (i = 0; i < V; ++i) {
+		printf("%d\t%d\n", i, dist[i]);
+	}
+	
+	return  0;
+}

misc/Factorial.c

@@ -1,20 +1,32 @@
 #include<stdio.h>
-
-int fat(int number){
-	if (number == 1 || number == 0) 
-		return 1;
-	else 
-		return number*fat(number-1);
+int main()
+{
+    int a[200],n,counter,temp,i;
+    a[0]=1;
+    counter=0;
+    printf("Enter a whole number to Find its Factorial: ");
+    scanf("%d",&n);
+   if(n<0)
+    printf("Cannot Calculate factorials for negative numbers.");
+   else{
+    for(; n>=2; n--)
+    {
+        temp=0;
+        for(i=0; i<=counter; i++)
+        {
+            temp=(a[i]*n)+temp;
+            a[i]=temp%10;
+            temp=temp/10;
+        }
+        while(temp>0)
+        {
+            a[++counter]=temp%10;
+            temp=temp/10;
+        }
+    }
+    for(i=counter; i>=0; i--)
+        printf("%d",a[i]);
 	}
-
-int main(){
-	int number;
-
-	//Asks the factorial of the number n 
-	printf("Number: ");
-	scanf("%d", &number);
-	
-	printf("%d\n", fat(number));
-	
     return 0;
+
 }