C Program for Traversing Undirected Graph through DFS Recursively

By | June 29, 2017

Traversing Undirected Graph through DFS Recursively


Write a C Program for Traversing Undirected Graph through DFS Recursively. Here’s simple Program for Traversing an Undirected Graph through DFS Recursively in C Programming Language.


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 Directed Graph through DFS and classifying all edges

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


SOURCE CODE : :


/* C Program for Traversing Undirected Graph through DFS Recursively */

#include<stdio.h>
#define MAX 100

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

int adj[MAX][MAX];

int n;    /* Denotes number of vertices in the graph */

int state[MAX];
int predecessor[MAX];

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

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;
		predecessor[v] = -1;
	}
	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);
	}
}/*End of DF_Traversal()*/

void DFS(int v)
{
	int i;
	state[v] = visited;
	printf("%d  ",v);
	for(i=0; i<n; i++)
	{
		if(adj[v][i] == 1)
		{
			if(state[i] == initial)
				DFS(i);
		}
	}
	state[v] = finished;
}/*End of DFS()*/


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

	printf("Enter number of vertices : ");
	scanf("%d",&n);
	max_edges = n*(n-1)/2;

	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;
			adj[destin][origin] = 1;
		}
	}
}

OUTPUT : :


/* C Program for Traversing Undirected Graph through DFS Recursively */

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 ) : 2 4

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

Enter edge 6( -1 -1 to quit ) : 1 5

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

Enter starting vertex for Depth First Search : 0
0  1  5  3  2  4

Process returned 0

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