bfs.cpp

#include <bits/stdc++.h>
using namespace std;
const int N = 1e5;

int visited[N];
vector<int>adj_list[N];

void bfs(int src){
    queue<int>q;

    visited[src] = 1;
    q.push(src);

    while(!q.empty()){
        int head = q.front();
        q.pop();

        cout<<head<<endl;
        for(int adj_node: adj_list[head]){
            if(visited[adj_node] == 0){
                visited[adj_node] = 1;
                q.push(adj_node);
            }
        }
    }
}

/*

0 --- 1     2 --- 3
      |     |
      |     |
      5 --- 4

no of node -> 6
no of edge -> 6

list of adj node -> 
0 1
2 3
1 5
2 4
5 4

*/

int main()
{
    int nodes, edges;
    cin>>nodes>>edges;

    for(int i=0; i<edges; i++){
        int u,v;
        cin>>u>>v;
        adj_list[u].push_back(v);
        adj_list[v].push_back(u);
    }

    int src = 0;
    bfs(src);

    return 0;
}


/*
6 5

0 1
2 3
1 5
2 4
5 4
*/