C program for implementation of graph : Creation of adjacency matrix and checking connections

".C" file is available in downloadable format at :

https://drive.google.com/file/d/0ByF0OId1bLx6WWZkeG53d3V6Wmc/view

(Open the link and click on the download arrow on the top right to download the file.)

Given Below is the code for implementation of stack using Linked List:

---------------------------------------------------------------------------------

#include<stdio.h>

#include<stdlib.h>

#define M 5

void readgraph ();

int a[M][M];

void main ()

{

int s,t, choice;

printf("\nHello and Welcome to graphs.\n\n");

printf("\nFirst of all, enter the graph");

readgraph();

while (1)

{

printf("\n\n1.Check connections\n2.Exit\nYour choice : ");

scanf("%d", &choice);

switch (choice)

 {

case 1:

{

printf("\nEnter the indices to check whether points A and B are connected or not : ");

printf("\nFirst Index:   "); scanf("%d", &s);

printf("\nSecond Index:   "); scanf("%d", &t);

if ( a[s][t] == 1 )

printf("\n Yes, they are connected");

else 

printf("\n No, they are not connected");

}

case 2 : 

exit(0);

default : 

printf("\nEnter valid option");

}

}

void readgraph ()

{

int i,j, choice, num;

printf("\nWhat's the number of entries?\nWell, it's : ");

scanf("%d", &num);

printf ("\nKey in 1 for Yes and 0 for No");

for(i=1; i<=num; i++)

{

for (j=1; j<=num; j++)

{

if (i==j)

a[i][j] =0;

else

{

printf("\nIs %d connected to %d : ", i,j);

scanf("%d", &choice);

if (choice==1)

a[i][j] = 1;

else

a[i][j] = 0;

}

}

}

return;

}