Programming: C Program to Represent Graph Using Adjacency Matrix

This C program generates graph using Adjacency Matrix Method.

A graph G,consists of two sets V and E. V is a finite non-empty set of vertices.E is a set of pairs of vertices,these pairs are called as edges V(G) and E(G) will represent the sets of vertices and edges of graph G.

Undirected graph – It is a graph with V vertices and E edges where E edges are undirected. In undirected graph, each edge which is present between the vertices Vi and Vj,is represented by using a pair of round vertices (Vi,Vj).

Directed graph – It is a graph with V vertices and E edges where E edges are directed.In directed graph,if Vi and Vj nodes having an edge.than it is represented by a pair of triangular brackets Vi,Vj.

Here is the source code of the C program to create a graph using adjacency matrix. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

//... A Program to represent a Graph by using an Adjacency Matrix method
#include 
#include 
int dir_graph();
int undir_graph();
int read_graph(int adj_mat[50][50], int n );

void main()
{
   int option;
   do
   {     
        printf("\n A Program to represent a Graph by using an ");
  printf("Adjacency Matrix method \n ");
  printf("\n 1. Directed Graph ");
  printf("\n 2. Un-Directed Graph ");
  printf("\n 3. Exit ");
  printf("\n\n Select a proper option : ");
  scanf("%d", &option);
  switch(option)
  {
    case 1 : dir_graph();
       break;
    case 2 : undir_graph();
       break;
    case 3 : exit(0);
  } // switch
    }while(1);
}
 
int dir_graph()
{
    int adj_mat[50][50];
    int n;
    int in_deg, out_deg, i, j;
    printf("\n How Many Vertices ? : ");
    scanf("%d", &n);
    read_graph(adj_mat, n);
    printf("\n Vertex \t In_Degree \t Out_Degree \t Total_Degree ");
    for (i = 1; i <= n ; i++ )
    {
        in_deg = out_deg = 0;
 for ( j = 1 ; j <= n ; j++ )
 {
            if ( adj_mat[j][i] == 1 )
                in_deg++;
 } 
        for ( j = 1 ; j <= n ; j++ )
            if (adj_mat[i][j] == 1 )
                out_deg++;
            printf("\n\n %5d\t\t\t%d\t\t%d\t\t%d\n\n",i,in_deg,out_deg,in_deg+out_deg);
    }
    return;
}
 
int undir_graph()
{
    int adj_mat[50][50];
    int deg, i, j, n;
    printf("\n How Many Vertices ? : ");
    scanf("%d", &n);
    read_graph(adj_mat, n);
    printf("\n Vertex \t Degree ");
    for ( i = 1 ; i <= n ; i++ )
    {
        deg = 0;
        for ( j = 1 ; j <= n ; j++ )
            if ( adj_mat[i][j] == 1)
                deg++;
        printf("\n\n %5d \t\t %d\n\n", i, deg);
    } 
    return;
} 
 
int read_graph ( int adj_mat[50][50], int n )
{
    int i, j;
    char reply;
    for ( i = 1 ; i <= n ; i++ )
    {
        for ( j = 1 ; j <= n ; j++ )
        {
            if ( i == j )
            {
                adj_mat[i][j] = 0;
  continue;
            } 
            printf("\n Vertices %d & %d are Adjacent ? (Y/N) :",i,j);
            scanf("%c", &reply);
            if ( reply == 'y' || reply == 'Y' )
                adj_mat[i][j] = 1;
            else
                adj_mat[i][j] = 0;
 }
    } 
    return;
}

$ gcc graph.c -o graph
$ ./graph
 A Program to represent a Graph by using an Adjacency Matrix method 
 
 1. Directed Graph 
 2. Un-Directed Graph 
 3. Exit 
 
 Select a proper option : 
 How Many Vertices ? : 
 Vertices 1 & 2 are Adjacent ? (Y/N) : N
 Vertices 1 & 3 are Adjacent ? (Y/N) : Y
 Vertices 1 & 4 are Adjacent ? (Y/N) : Y
 Vertices 2 & 1 are Adjacent ? (Y/N) : Y
 Vertices 2 & 3 are Adjacent ? (Y/N) : Y
 Vertices 2 & 4 are Adjacent ? (Y/N) : N
 Vertices 3 & 1 are Adjacent ? (Y/N) : Y
 Vertices 3 & 2 are Adjacent ? (Y/N) : Y
 Vertices 3 & 4 are Adjacent ? (Y/N) : Y
 Vertices 4 & 1 are Adjacent ? (Y/N) : Y
 Vertices 4 & 2 are Adjacent ? (Y/N) : N
 Vertices 4 & 3 are Adjacent ? (Y/N) : Y
 Vertex   In_Degree   Out_Degree   Total_Degree 
 
     1   2  0  2
 
 
 
     2   1  2  3
 
 
 
     3   0  1  1
 
 
 
     4   1  1  2
 
 
 A Program to represent a Graph by using an Adjacency Matrix method 
 
 1. Directed Graph 
 2. Un-Directed Graph 
 3. Exit