Add Floyd-Warshall Algorithm

data_structures/graphs/Floyd-Warshall.c

@@ -0,0 +1,104 @@
+#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 print distances
+void print(int dist[], int V){
+	printf("\nThe Distance matrix for Floyd - Warshall\n");
+	for(int i = 0; i < V; i++){
+		for(int j=0; j<V; j++){
+
+		if(dist[i*V+j] != INT_MAX)	
+			printf("%d\t",dist[i*V+j]);
+		else
+			printf("INF\t");
+		}
+		printf("\n");
+	}
+}
+
+//The main function that finds the shortest path from a vertex
+//to all other vertices using Floyd-Warshall Algorithm.
+void FloydWarshall(struct Graph* graph){
+	int V = graph->vertexNum;
+	int dist[V][V];
+	
+	//Initialise distance array
+	for(int i=0; i<V; i++)
+		for(int j=0; j<V; j++)
+			dist[i][j] = graph->edges[i][j];	
+			
+	
+	//Calculate distances
+	for(int k=0; k<V; k++)
+	//Choose an intermediate vertex
+
+		for(int i=0; i<V; i++)	
+		//Choose a source vertex for given intermediate
+
+			for(int j=0; j<V; j++)
+			//Choose a destination vertex for above source vertex
+
+				if(dist[i][k] != INT_MAX && dist[k][j] != INT_MAX && dist[i][k] + dist[k][j] < dist[i][j])
+				//If the distance through intermediate vertex is less than direct edge then update value in distance array
+					dist[i][j] = dist[i][k] + dist[k][j];
+
+	
+	//Convert 2d array to 1d array for print
+	int dist1d[V*V];	
+	for(int i=0; i<V; i++)
+		for(int j=0; j<V; j++)
+			dist1d[i*V+j] = dist[i][j];
+	
+	print(dist1d,V);	
+	}
+
+//Driver Function
+int main(){
+	int V,E;
+	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);
+	}
+	FloydWarshall(&G);
+
+	return 0;
+}