From 909f00c6051eedb43ec4feaacf5cb6c1e22aee02 Mon Sep 17 00:00:00 2001
From: arpanjain97 <arpanjain97@gmail.com>
Date: Thu, 12 Oct 2017 21:03:44 +0530
Subject: [PATCH] Add Dijkstra's Algorithm

---
 data_structures/graphs/Dijkstra.c | 110 ++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 data_structures/graphs/Dijkstra.c

diff --git a/data_structures/graphs/Dijkstra.c b/data_structures/graphs/Dijkstra.c
new file mode 100644
index 00000000..fc278b76
--- /dev/null
+++ b/data_structures/graphs/Dijkstra.c
@@ -0,0 +1,110 @@
+#include<stdio.h>
+#include<stdlib.h>
+#include<limits.h>
+#include<string.h>
+
+
+//Structure for storing a graph
+struct Graph{
+	int vertexNum;
+	int** edges;
+};
+
+//Constructs a graph with V vertices and E edges
+void createGraph(struct Graph* G,int V){
+		G->vertexNum = V;
+		G->edges =(int**) malloc(V * sizeof(int*));
+		for(int i=0; i<V; i++){
+			G->edges[i] = (int*) malloc(V * sizeof(int));
+			for(int j=0; j<V; j++)
+				G->edges[i][j] = INT_MAX;
+			G->edges[i][i] = 0;
+		}		
+}
+
+//Adds the given edge to the graph 
+void addEdge(struct Graph* G, int src, int dst, int weight){
+	G->edges[src][dst] = weight;
+}
+
+
+//Utility function to find minimum distance vertex in mdist
+int minDistance(int mdist[], int vset[], int V){
+	int minVal = INT_MAX, minInd ;
+	for(int i=0; i<V;i++)
+		if(vset[i] == 0 && mdist[i] < minVal){
+		minVal = mdist[i];
+		minInd = i;
+		}
+			
+	return minInd;
+}
+
+//Utility function to print distances
+void print(int dist[], int V){
+	printf("\nVertex  Distance\n");
+	for(int i = 0; i < V; i++)
+		printf("%d\t%d\n",i,dist[i]);
+}
+
+//The main function that finds the shortest path from given source
+//to all other vertices using Dijkstra's Algorithm.It doesn't work on negative
+//weights
+void Dijkstra(struct Graph* graph, int src){
+	int V = graph->vertexNum;
+	int mdist[V];   //Stores updated distances to vertex
+	int vset[V];    // vset[i] is true if the vertex i included
+			// in the shortest path tree
+
+	//Initialise mdist and vset. Set distance of source as zero
+	for(int i=0; i<V; i++)
+		mdist[i] = INT_MAX, vset[i] = 0;
+	
+	mdist[src] = 0;
+	
+	//iterate to find shortest path
+	for(int count = 0; count<V-1; count++){
+		int u = minDistance(mdist,vset,V);
+		vset[u] = 1;
+		
+		for(int v=0; v<V; v++){
+			if(!vset[v] && graph->edges[u][v]!=INT_MAX && mdist[u] + graph->edges[u][v] < mdist[v])
+				mdist[v] = mdist[u] + graph->edges[u][v];
+				
+		}
+	}
+
+	print(mdist, V);
+	
+	return;
+}
+
+
+
+//Driver Function
+int main(){
+	int V,E,gsrc;
+	int src,dst,weight;
+	struct Graph G;
+	printf("Enter number of vertices: ");
+	scanf("%d",&V);
+	printf("Enter number of edges: ");
+	scanf("%d",&E);
+	createGraph(&G,V);
+	for(int i=0; i<E; i++){
+		printf("\nEdge %d \nEnter source: ",i+1);
+		scanf("%d",&src);
+		printf("Enter destination: ");
+		scanf("%d",&dst);
+		printf("Enter weight: ");
+		scanf("%d",&weight);
+		addEdge(&G, src, dst, weight);
+	}
+	printf("\nEnter source:");
+	scanf("%d",&gsrc);
+	Dijkstra(&G,gsrc);
+
+	return 0;
+}
+
+