OSPF.c

#include<stdio.h>

void shortest_path(int n , int cost[n][n] , int src) 
{ 
    int dist[n];
    int visited[n];
    int i;
    int last[n];
    int count;
  
    for (i = 0; i < n ; i++)
    {
        dist[i] = 1000;
		visited[i] = 0;
		last[i] = src;
	}
	 
    dist[src] = 0; 

    for (count = 0 ; count < n-1 ; count++)
	{ 
        int min = 1000;
        int u; 
  		for (i = 0 ; i < n ; i++) 
    	{
        	if (visited[i] == 0 && dist[i]<= min)
        	{
            	min = dist[i];
				u = i; 
			}
		}
		 
        visited[u] = 1;
		 
        for (i = 0;i < n ; i++) 
        { 
            if (visited[i] == 0 && dist[u] + cost[u][i] < dist[i]) 
            {
                dist[i] = dist[u] + cost[u][i];

                if(last[i] == src)
                {
                	last[i] = u;
                }
        	}
    	}
    } 
    
    
    printf(" Routing Table of Node %d \n" , src + 1);

	printf("Destination\tCost\tNext Hop \n");

    for(i = 0 ; i < n ; i++)
	{
		if(i == src - 1)
		{
			printf("  %d\t\t - \t\t - \n", src + 1);
		}
		else
		{
			if(last[i] == src)
			{
				printf("  %d\t\t%d\t\t-\n", i + 1, dist[i]);
			}
			else
				printf("  %d\t\t%d\t\t%d\n", i + 1, dist[i] , last[i] + 1);
		}
	}
	
	printf("\n");

	for(i = 0;i < n ; i++)
	{
		if(i != src)
		{
			printf(" The cost of the shortest path from router %d to %d is %d\n", src + 1 , i + 1 , dist[i]);
		}
	}
} 

int main()
{
	int n;
	int i;
	int j;
	int src;
	printf("Enter the Number of Nodes : ");

	scanf("%d",&n);
	
	int cost[n][n];

	printf(" Enter the cost between Nodes : \n");

	for(i = 0; i < n ; i++)
	{
		for(j = 0 ;j < n ; j++)
		{
			if(i != j)
			{
				printf("Cost from %d->%d : ",i + 1 ,j + 1);

				scanf("%d",&cost[i][j]);

				if(cost[i][j] == 0)
				{
					cost[i][j] = 1000;
				}
			}
			else
			{
				cost[i][j] = 0;
			}
		}
	}

	printf(" Enter the source Node : ");

	scanf("%d",&src);
	
	printf("Routing Table of Node %d\n",src);

	printf("Destination\tCost\tNext Hop\n");

	for(i = 0; i < n ; i++)
	{
		if(i == src - 1)
		{
			printf("  %d\t\t-\t\t-\n",src);
		}
		else
		{
			if(cost[src-1][i] == 0)
			{
				printf("  %d\t\t-\t\t- \n",i+1);
			}
			else
			{
				printf("  %d\t\t%d\t\t-\n",i+1,cost[src-1][i]);
			}
		}
	}
	
	printf("After Applying Dijkstra's Algorithm\n\n");
	
	shortest_path(n , cost , src-1);

	return 0;
}