DFS

#include <bits/stdc++.h>
using namespace std;

void dfs(int source, vector<bool> &visited, vector<vector<int> > &adj){

    //level = source
    //options = neighbours of source

    //mark source visited
    visited[source] = true;
    cout << source << " ";
    for(int i = 0; i < adj[source].size(); i++){
        int node = adj[source][i];
        if(!visited[node]){
            dfs(node, visited, adj);
        }
    }

}

int main() {
    // your code goes here
    int n, m;
    cin >> n >> m;

    vector<vector<int> > adj(n + 1, vector<int>());

    for(int i = 0; i < n; i++){
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    vector<bool> visited(n + 1, false);
    int source = 1;
    dfs(source, visited, adj);
}