TheAlgorithms-C/data_structures/graphs/Floyd-Warshall.c

#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;
}