Merge pull request #268 from kaustavbhattacharya07/master

Added Max Heap Data Structure

data_structures/heap/maxheap.c

@@ -0,0 +1,121 @@
+#include<stdio.h>
+#include<stdlib.h>
+
+typedef struct max_heap{
+	int *p;
+	int size;
+	int count;
+}Heap;
+
+Heap* create_heap(Heap* heap); /*Creates a max_heap structure and returns a pointer to the struct*/
+void down_heapify(Heap* heap, int index);/*Pushes an element downwards in the heap to find its correct position*/
+void up_heapify(Heap* heap, int index);/*Pushes an element upwards in the heap to find its correct position*/
+void push(Heap* heap, int x);/*Inserts an element in the heap*/
+void pop(Heap* heap);/*Removes the top element from the heap*/
+int top(Heap* heap);/*Returns the top element of the heap or returns INT_MIN if heap is empty*/
+int empty(Heap* heap);/*Checks if heap is empty*/
+int size(Heap* heap);/*Returns the size of heap*/
+
+int main(){
+	Heap* head = create_heap(head);
+	push(head, 10);
+	printf("Pushing element : 10\n");
+	push(head, 3);
+	printf("Pushing element : 3\n");
+	push(head, 2);
+	printf("Pushing element : 2\n");
+	push(head, 8);
+	printf("Pushing element : 8\n");
+	printf("Top element = %d \n", top(head));
+	push(head, 1);
+	printf("Pushing element : 1\n");
+	push(head, 7);
+	printf("Pushing element : 7\n");
+	printf("Top element = %d \n", top(head));
+	pop(head);
+	printf("Popping an element.\n");
+	printf("Top element = %d \n", top(head));
+	pop(head);
+	printf("Popping an element.\n");
+	printf("Top element = %d \n", top(head));
+	printf("\n");
+	return 0;
+}
+Heap* create_heap(Heap* heap){
+	heap = (Heap *)malloc(sizeof(Heap));
+	heap->size = 1;
+	heap->p = (int *)malloc(heap->size*sizeof(int));
+	heap->count = 0;
+}
+
+void down_heapify(Heap* heap, int index){
+	if(index>=heap->count)return;
+	int left = index*2+1;
+	int right = index*2+2;
+	int leftflag = 0, rightflag = 0;
+	
+	int maximum = *((heap->p)+index);
+	if(left<heap->count && maximum<*((heap->p)+left)){
+		maximum = *((heap->p)+left);
+		leftflag = 1;
+	}
+	if(right<heap->count && maximum<*((heap->p)+right)){
+		maximum = *((heap->p)+right);
+		leftflag = 0;
+		rightflag = 1;
+	}
+	if(leftflag){
+		*((heap->p)+left) = *((heap->p)+index);
+	    *((heap->p)+index) = maximum;
+	    down_heapify(heap, left);
+	}
+	if(rightflag){
+		*((heap->p)+right) = *((heap->p)+index);
+	    *((heap->p)+index) = maximum;
+	    down_heapify(heap, right);
+	}
+}
+void up_heapify(Heap* heap, int index){
+	int parent = (index-1)/2;
+	if(parent<0)return;
+	if(*((heap->p)+index)>*((heap->p)+parent)){
+		int temp = *((heap->p)+index);
+		*((heap->p)+index) = *((heap->p)+parent);
+		*((heap->p)+parent) = temp;
+		up_heapify(heap, parent);
+	}
+}
+
+void push(Heap* heap, int x){
+	if(heap->count>=heap->size)return;
+	*((heap->p)+heap->count) = x;
+	heap->count++;
+	if(4*heap->count >= 3*heap->size){
+		heap->size *= 2;
+		(heap->p) = (int *)realloc((heap->p), (heap->size)*sizeof(int));
+	}
+	up_heapify(heap, heap->count - 1);
+}
+void pop(Heap* heap){
+	if(heap->count==0)return;
+	heap->count--;
+	int temp = *((heap->p)+heap->count);
+	*((heap->p)+heap->count) = *(heap->p);
+	*(heap->p) = temp;
+	down_heapify(heap, 0);
+	if(4*heap->count<=heap->size){
+		heap->size /= 2;
+		(heap->p) = (int *)realloc((heap->p), (heap->size)*sizeof(int));
+	}
+}
+int top(Heap* heap){
+	if(heap->count!=0)return *(heap->p);
+	else return INT_MIN;
+}
+int empty(Heap* heap){
+	if(heap->count!=0)return 0;
+	else return 1;
+}
+int size(Heap* heap){
+	return heap->count;
+}