C Program for Traversing Directed Graph through DFS and classifying all edges

By | 25.06.2017

Directed Graph through DFS and classifying all edges


Write a C Program for Traversing Directed Graph through DFS and classifying all edges. Here’s simple Program for Traversing Directed Graph through DFS and classifying all edges.


Depth First Search (DFS)


Depth First Search (DFS) algorithm traverses a graph in a depthward motion and uses a stack to remember to get the next vertex to start a search, when a dead end occurs in any iteration.

It employs the following rules.

  • Rule 1 − Visit the adjacent unvisited vertex. Mark it as visited. Display it. Push it in a stack.
  • Rule 2 − If no adjacent vertex is found, pop up a vertex from the stack. (It will pop up all the vertices from the stack, which do not have adjacent vertices.)
  • Rule 3 − Repeat Rule 1 and Rule 2 until the stack is empty.

We shall not see the implementation of Depth First Traversal (or Depth First Search) in C programming language


Also Read : : C Program for traversing a Directed Graph through DFS recursively

Below is the source code for C Program for Traversing Directed Graph through DFS and classifying all edges in output which is successfully compiled and run on Windows System to produce desired output as shown below :


SOURCE CODE : :


/* C Program for Traversing Directed Graph through DFS and classifying all edges */

#include<stdio.h>
#define MAX 50

#define initial 1
#define visited 2
#define finished 3

int n;    /*Number of vertices in the graph */
int adj[MAX][MAX];
void create_graph( );

int state[MAX];
int time;
int d[MAX];
int f[MAX];

void DF_Traversal();
void DFS(int v);

int main()
{
        create_graph();
        DF_Traversal();
        return 0;
}/*End of main()*/

void DF_Traversal()
{
        int v;

        for(v=0; v<n; v++)
                state[v] = initial;

        printf("\nEnter starting vertex for Depth First Search : ");
        scanf("%d",&v);
        DFS(v);
        for(v=0; v<n; v++)
        {
                if(state[v] == initial)
                        DFS(v);
        }
        printf("\n");
}/*End of DF_Traversal( )*/


void DFS(int v)
{
        int i;
        time++;
        d[v] = time;
        state[v] = visited;

        for(i=0; i<n; i++)
        {
                if(adj[v][i] == 1)
                {
                        if(state[i] == initial)
                        {
                                printf("\n(%d,%d) - Tree edge\n", v, i);
                                DFS(i);
                        }
                        else if(state[i] == visited)
                        {
                                printf("\n(%d,%d) - Back edge\n", v, i);
                        }
                        else if(d[v] < d[i])
                        {
                                printf("\n(%d,%d) - Forward edge\n", v, i);
                        }
                        else
                                printf("\n(%d,%d) - Cross edge\n", v, i);
                }
        }
        state[v] = finished;
        f[v] = ++time;
}/*End of DFS()*/

void create_graph()
{
        int i,max_edges,origin,destin;

        printf("\nEnter number of vertices : ");
        scanf("%d",&n);
        max_edges=n*(n-1);

        for(i=1;i<=max_edges;i++)
        {
                printf("\nEnter edge %d( -1 -1 to quit ) : ",i);
                scanf("%d %d",&origin,&destin);

                if( (origin == -1) && (destin == -1) )
                        break;

                if( origin >= n || destin >= n || origin<0 || destin<0)
                {
                        printf("\nInvalid edge!\n");
                        i--;
                }
                else
                {
                        adj[origin][destin] = 1;
                }
        }
}

OUTPUT : :


/* C Program for Traversing Directed Graph through DFS and classifying all edges */

Enter number of vertices : 6

Enter edge 1( -1 -1 to quit ) : 0 1

Enter edge 2( -1 -1 to quit ) : 0 2

Enter edge 3( -1 -1 to quit ) : 0 3

Enter edge 4( -1 -1 to quit ) : 0 4

Enter edge 5( -1 -1 to quit ) : 1 3

Enter edge 6( -1 -1 to quit ) : 3 4

Enter edge 7( -1 -1 to quit ) : 2 5

Enter edge 8( -1 -1 to quit ) : 5 4

Enter edge 9( -1 -1 to quit ) : -1 -1

Enter starting vertex for Depth First Search : 0

(0,1) - Tree edge

(1,3) - Tree edge

(3,4) - Tree edge

(0,2) - Tree edge

(2,5) - Tree edge

(5,4) - Cross edge

(0,3) - Forward edge

(0,4) - Forward edge


Process returned 0

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