bfs.cpp

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+7;
vector<int>adj[N];
bool visited[N];
int level[N];

void bfs(int node){
    queue<int>q;
    q.push(node);
    visited[node]=true;
    while(!q.empty()){
        int current_vertex=q.front();
        q.pop();
        for(auto child : adj[current_vertex]){
            if(!visited[child]){
                q.push(child);
                visited[child]=true;
                level[child]=level[current_vertex]+1;
            }
        }
    }
}
int main(){
    int n;
    cin>>n;
    memset(visited,false,sizeof(visited));
    for(int i=0;i<n-1;i++){
        int a,b;
        cin>>a>>b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    bfs(1);
}