ALGR: DFS

/*
*   Masfiq
*   17 Apr, 2017
*/
#include<iostream>
#include<cstdio>
#include<vector>
using namespace std;

void DFS_utility(vector<vector<int>> gr, vector<int> &color, int src);

void DFS(vector<vector<int>> gr, int src){
    int nv = gr.size();
    vector<int> color(nv, 0);//0=white/unvisited,  1=grey/visiting its children,  2=black/visited
    DFS_utility(gr,color,src);
}
void DFS_utility(vector<vector<int>> gr, vector<int> &color, int src){// taking reference to see the changes in color
    int u=src;
    color[u]=1;//making grey/visiting its children
    for(int i=0;i<gr[u].size();i++){
        int v=gr[u][i];
        if(color[v]==0)
            DFS_utility(gr,color,v);
    }
    color[u]=2;//making black/visited
}

int main()
{
    int n, e;
    scanf("%d %d", &n, &e);
    vector<vector<int>> gr;
    gr.clear();
    gr.resize(n+1);
    for(int i=0; i<e; i++)
    {
        int u,v;
        scanf("%d %d", &u, &v);
        gr[u].push_back(v);
        gr[v].push_back(u);
    }
    DFS(gr, 1);
    return 0;
}