adj_crea.c

Graph Programs in C

/* Program for creation of adjacency matrix */
#include<stdio.h>
#define max 20

int adj[max][max]; /*Adjacency matrix */
int n;    /* Denotes number of nodes in the graph */
main()
{
	int max_edges,i,j,origin,destin;
	char graph_type;

	printf("Enter number of nodes : ");
	scanf("%d",&n);
	printf("Enter type of graph, directed or undirected (d/u) : ");
	fflush(stdin);
	scanf("%c",&graph_type);

	if(graph_type=='u')
		max_edges=n*(n-1)/2;
	else
		max_edges=n*(n-1);

	for(i=1;i<=max_edges;i++)
	{
		printf("Enter edge %d( 0 0 to quit ) : ",i);
		scanf("%d %d",&origin,&destin);
		if( (origin==0) && (destin==0) )
			break;
		if( origin > n || destin > n || origin<=0 || destin<=0)
		{
			printf("Invalid edge!\n");
			i--;
		}
		else
		{
			adj[origin][destin]=1;
			if( graph_type=='u')
				adj[destin][origin]=1;
		}
	}/*End of for*/

	printf("The adjacency matrix is :\n");
	for(i=1;i<=n;i++)
	{
		for(j=1;j<=n;j++)
			printf("%4d",adj[i][j]);
		printf("\n");
	}
}/*End of main()*/