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link_state_routing.c
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link_state_routing.c
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#include <stdio.h>
int main()
{
int n; // number of routers
int source; //source router
int cost[20][20]; // cost matrix
int flag[20];// indicate wether we visited a node
int distance[20];// distance of node from source
int previous[20];// previous node of a node
printf("\nEnter the number of routers: ");
scanf("%d", &n);
printf("\nEnter the cost matrix: \n\n");
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++)
{
scanf("%d", &cost[i][j]);
// setting a large value for negative cost (indicate there is no direct connection or path)
if(cost[i][j] < 0)
{
cost[i][j] = 10000;
}
}
}
printf("Enter the source router: ");
scanf("%d", &source);
for(int i=0;i<n;i++)
{
flag[i] = 0;
previous[i] = source;
distance[i] = cost[source][i];
}
flag[source] = 1; // visit source router
int min_distance;
int min_node;
for(int i=0; i<n-1; i++)
{
min_distance = 10000;
for(int j=0;j<n;j++)
{
if(!flag[j] && distance[j]<min_distance)
{
min_node = j;
min_distance = distance[j];
}
}
flag[min_node] = 1; // visit the node with minimum distance from current node.
for(int j=0;j<n;j++)
{
if(!flag[j] && (min_distance + cost[min_node][j]<distance[j]))
{
distance[j] = min_distance + cost[min_node][j];
previous[j] = min_node;
}
}
}
int temp;
// Printing the result
for(int i=0 ; i<n ; i++)
{
printf("\n\n%d --> %d\nPath Taken: %d", source, i, i);
temp = i;
while(temp != source)
{
printf(" <-- %d", previous[temp]);
temp = previous[temp];
}
printf("\n Shortest Path Cost: %d", distance[i]);
}
return 0;
}