Graph Representation using 2D Arrays in C

This is a C Program to generates graph using 2D Array. 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 source code of the C Program to Represent Graph Using 2D Arrays. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
#include <stdio.h>
```
```
#include <stdlib.h>
```
```
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;
```
```
}
```

Output:

$ gcc GraphUsingTwoDMatrix.c
$ ./a.out
 
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

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