atleast_bell.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define INT_MAX 100000
struct Edge
{
    int src, dest, weight;
};
struct Graph
{
    int V, E;
    struct Edge* edge;
};
struct Graph* createGraph(int V, int E)
{
    struct Graph* graph = (struct Graph *) malloc(sizeof(struct Graph));
    graph->V = V;
    graph->E = E;
    graph->edge = (struct Edge *)malloc(sizeof(struct Edge)*E);
    return graph;
}
void printArr(int dist[5][5], int n)
{
    printf("Vertex   Distance from Source atleast 2 hops\n");
        for (int j = 0; j < n; ++j)
        {
            printf(" \t %d", dist[4][j]);
        }
            printf("\n");
     
        
 }
void BellmanFord(struct Graph* graph, int src,int length)
{
    int V = graph->V;
    int E = graph->E;
    int dist[V][V];
    for (int i = 0; i < V; i++)
        for (int j = 0; j < V; ++j)
        {
            dist[i][j]   = INT_MAX;
        }  
    dist[0][src] = 0;
    int temp;
    for (int i = 1; i <= length; i++)
    {
        for (int j = 0; j < E; j++)
        {
            int u = graph->edge[j].src;
            int v = graph->edge[j].dest;
            int weight = graph->edge[j].weight;
            if (dist[i-1][u] != INT_MAX )
                dist[i][v] = dist[i-1][u] + weight;
        }
        temp=i+1;
    }
    for ( int i=temp ; i <= V-1; i++)
    {
        for (int j = 0; j < E; j++)
        {
            int u = graph->edge[j].src;
            int v = graph->edge[j].dest;
            int weight = graph->edge[j].weight;
            if (dist[i-1][u] != INT_MAX && dist[i-1][u] + weight < dist[i-1][v])
                dist[i][v] = dist[i-1][u] + weight;
            else if(dist[i][v]>dist[i-1][v])
                dist[i][v]=dist[i-1][v];
        }
    }
    printArr(dist, V);
 
    return;
}
int main()
{
    
    int V = 5;  
    int E = 8;  
    struct Graph* graph = createGraph(V, E);
    graph->edge[0].src = 0;
    graph->edge[0].dest = 1;
    graph->edge[0].weight = 1;
 
    graph->edge[1].src = 0;
    graph->edge[1].dest = 2;
    graph->edge[1].weight = 4;
 
    graph->edge[2].src = 1;
    graph->edge[2].dest = 2;
    graph->edge[2].weight = 3;

    graph->edge[3].src = 1;
    graph->edge[3].dest = 3;
    graph->edge[3].weight = 2;
 
    graph->edge[4].src = 1;
    graph->edge[4].dest = 4;
    graph->edge[4].weight = 2;
 
    graph->edge[5].src = 3;
    graph->edge[5].dest = 2;
    graph->edge[5].weight = 5;
 
    graph->edge[6].src = 3;
    graph->edge[6].dest = 1;
    graph->edge[6].weight = 1;

    graph->edge[7].src = 4;
    graph->edge[7].dest = 3;
    graph->edge[7].weight = -3;
 
    BellmanFord(graph, 0,2);
    return 0;
}