# Program of Breadth First Search Traversal ( BFS )

```#include <iostream.h>
#include <conio.h>
#define MAX_NODE 50

struct node{
int vertex;
node *next;
};

int totNodes; //No. of Nodes in Graph.

////////////Queue Operation\\\\\\\\\\\\\\\\\\\\\\\\    int queue[MAX_NODE],f=-1,r=-1;

void q_insert(int item){
r = r+1;
queue[r]=item;
if(f==-1)
f=0;
}

int q_delete(){
int delitem=queue[f];
if(f==r)
f=r=-1;
else
f=f+1;
return(delitem);
}

int is_q_empty(){
if(f==-1)
return(1);
else
return(0);
}
////////////Queue Operation\\\\\\\\\\\\\\\\\\\\\\\\
void createGraph(){
node *newl,*last;
int neighbours,neighbour_value;
cout<<\"\\n\\n---Graph Creation---\\n\\n\";
cout<<\"Enter total nodes in graph : \";
cin>>totNodes;
for(int i=1;i<=totNodes;i++){
last=NULL;
cout<<\"\\nEnter no. of nodes in the adjacency list of node \"<<i<<\"\\n\";
cout<<\"--> That is Total Neighbours of \"<<i<<\" : \";
cin>>neighbours;
for(int j=1;j<=neighbours;j++){
cout<<\"Enter neighbour #\"<<j<<\" : \";
cin>>neighbour_value;
newl=new node;
newl->vertex=neighbour_value;
newl->next=NULL;
else{
last->next = newl;
last = newl;
}
}
}
}

void BFS_traversal(){
node *tmp;
int N,v,start_node,status[MAX_NODE];//status arr for maintaing status.
const int ready=1,wait=2,processed=3; //status of node.

cout<<\"Enter starting node : \";
cin>>start_node;

//step 1 : Initialize all nodes to ready state.
for(int i=1;i<=totNodes;i++)

//step 2 : put the start node in queue and change status.
q_insert(start_node); //Put starting node into queue.
status[start_node]=wait; //change it status to wait state.

//step 3 : Repeat until queue is empty.
while(is_q_empty()!=1){

//step 4 : Remove the front node N of queue.
//process N and change the status of N to
//be processed state.
N = q_delete(); //remove front node of queue.
status[N]=processed; //status of N to processed.
cout<<\"   \"<<N; //displaying processed node.

//step 5 : Add to rear of queue all the neighbours of N,
//that are in ready state and change their status to
//wait state.
tmp = adj[N];  //for status updation.
while(tmp!=NULL){
v = tmp->vertex;
q_insert(v); //insert N\'s neighbour who are in ready state.
status[v]=wait; //and make their status to wait state.
}
tmp=tmp->next;
}
}
}

void main(){
clrscr();