Breadth First Search ( BFS )

#include<stdio.h>
#include<stdlib.h>
#define max 20

void BFS(int adj[20][20],int n,int u);
void addq(int x);
int qempty();
int delq();

int front=-1,rear=-1;
int q[20];

void main()
{
    int adj[20][20],visited[10],n,u,v,i,j;

    printf("Enter no of vertices:");
    scanf("%d",&n);

    for(i=1; i<=n; i++)
    {   for(j=1; j<=n; j++)
        {
            adj[i][j]=0;
        }
    }
    printf("Enter edge:");
    scanf("%d%d",&u,&v);
    while(u!=0)
    {
        adj[u][v]=1;
        adj[v][u]=1;
        printf("Enter another edge:");
        scanf("%d%d",&u,&v);
    }
    printf("Enter starting vertex:");
    scanf("%d",&u);
    BFS(adj,n,u);
}

void BFS(int adj[20][20],int n,int u)
{
    int visited[10],v,i;
    for(i=1; i<=n; i++)
    {
        visited[i]=0;
    }

    addq(u);

    while(!qempty())
    {
        u=delq();
        visited[u]=1;
        printf("%d ",u);
        for(v=1; v<=n; v++)
        {
            if(adj[u][v]==1&&visited[v]==0)
            {
                addq(v);
                visited[v]=1;
            }
        }
    }
}


int qempty()
{   if(front==rear)
        return 1;
    else
        return 0;
}

int delq()
{
    int x;
    if(front==rear)
    {
        printf("Queue is empty\n");
        exit(0);
    }
    else
    {
        front=front+1;
        x=q[front];
        return x;
    }
}

void addq(int x)
{
    if(rear==max-1)
        printf("Queue is full\n");
    else
    {
        rear=rear+1;
        q[rear]=x;
    }
}

     

           

Note: Need to be arranged in compiler after copied

   

 OutPut:

Enter no of vertices:6 Enter edge:1 2 Enter another edge:1 3 Enter another edge:2 4 Enter another edge:2 5 Enter another edge:3 5 Enter another edge:4 5 Enter another edge:4 6 Enter another edge:5 6 Enter another edge:0 0 Enter starting vertex:1 1 2 3 4 5