Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	nNodes := scanInt(sc)
	nConns := scanInt(sc)

	graph := make([][]int, nNodes)
	for i := 0; i < nConns; i++ {
		a, b := scanInt(sc), scanInt(sc)
		graph[a] = append(graph[a], b)
		graph[b] = append(graph[b], a)
	}

	groups := make([]int, nNodes)

	var setGroups func(int, int)
	setGroups = func(u int, groupId int) {
		if groups[u] > 0 {
			return
		}
		groups[u] = groupId

		for _, v := range graph[u] {
			setGroups(v, groupId)
		}
	}
	for i := 0; i < nNodes; i++ {
		setGroups(i, i+1)
	}

	nQuestions := scanInt(sc)

	w := bufio.NewWriter(os.Stdout)
	var ans string
	for i := 0; i < nQuestions; i++ {
		a, b := scanInt(sc), scanInt(sc)
		if groups[a] == groups[b] {
			ans = "yes"
		} else {
			ans = "no"
		}
		fmt.Fprintln(w, ans)
	}
	w.Flush()
}

func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

C++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;

int n, m;
stack<int> S;
vector<int> V[100000];
int color[100000];

void dfs(int i, int id){
    S.push(i);
    color[i] = id;

    while(!S.empty()){
        int u = S.top();
        S.pop();
        for(int i=0; i<V[u].size(); i++){
            int v = V[u][i];
            if(color[v]==-1){
                color[v] = id;
                S.push(v);
            }
        }
    }
}

void dfs_init(){

    int id = 1; //グラフの識別
    for(int i=0; i<n; i++){
        color[i] = -1;
    }
    for(int i=0; i<n; i++){
        if(color[i]==-1) dfs(i, id++);
    }
}

int main(){

    cin >> n >> m;

    for(int i=0; i<m; i++){
        int a, b;
        cin >> a >> b;
        V[a].push_back(b);
        V[b].push_back(a);
    }

    dfs_init();

    int q;
    cin >> q;
    for(int i=0; i<q; i++){
    int x, y;
    cin >> x >> y;
    if(color[x]==color[y]) cout << "yes" << endl;
    else cout << "no" << endl;
    }

    return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct UnionFind{
    UnionFind(int size):_array(size, -1){
    }

    bool same(int x, int y){
        return root(x) == root(y);
    }

    void unify(int x, int y){
        int rootx = root(x);
        int rooty = root(y);
        if( rootx == rooty ){
            return;
        }
        if( size(rootx) < size(rooty) ) swap(rootx,rooty);
        _array[rootx] += _array[rooty];
        _array[rooty] = rootx;
    }

    int root(int x){
        if( _array[x] < 0 ){
            return x;
        }
        return _array[x] = root(_array[x]);
    }

    int size(int x){
        return -_array[root(x)];
    }

    vector<int> _array;
};

void DFS(vector<vector<int>>& graph, int v, vector<int>& visited, int root, UnionFind& uf){
    visited[v] = true;
    uf.unify(v, root);
    for(int i = 0 ; i < graph[v].size(); i++){
        if(visited[graph[v][i]] == false){
            DFS(graph, graph[v][i], visited, root, uf);
        }
    }
}

int main(){
    int n, m;
    cin >> n >> m;

    vector<vector<int>> graph(n);
    for(int i = 0; i < m; i++){
        int v1, v2;
        cin >> v1 >> v2;
        graph[v1].push_back(v2);
        graph[v2].push_back(v1);
    }

    vector<int> visited(n, false);
    UnionFind uf(n);

    for(int i = 0; i < n ; i++){
        if( visited[i] == false ){
            DFS(graph, i, visited, i, uf);
        }
    }

    int q;
    cin >> q;

    for(int i = 0; i < q; i++ ){
        int v1, v2;
        cin >> v1 >> v2;
        if( uf.same(v1, v2) ){
            cout << "yes" << endl;
        }else{
            cout << "no" << endl;
        }
    }

    return 0;

}

C++: //TLEになってしまった

#include<iostream>
#include<vector>
#include<utility>
using namespace std;
#define INF 1000000000

void dfs(vector< vector<int> >& rel,vector<int>& v,int c,int k){
  int l=rel[k].size();
  for(int i=0;i<l;i++){
    if(v[rel[k][i]]==0){
      v[rel[k][i]]=c;
      dfs(rel,v,c,rel[k][i]);
    }
  }
}


int main(){
  int n,m;cin >> n >> m;
  vector<int> v(n,0);//番号を記録(訪問済みでない場合は0)
  vector< vector<int> > rel(n);//隣接リスト

  //隣接リスト、Nodeの行列を作る必要ない
  for(int i=0;i<m;i++){
    int x,y;cin >> x >> y;
    rel[x].push_back(y);rel[y].push_back(x);
  }

  int col=0;
  for(int i=0;i<n;i++){
    if(v[i]==0){
      col++;
      dfs(rel,v,col,i);
    }
  }

  int q;cin >>q;
  for(int i=0;i<q;i++){
    int s,t;cin >> s >> t;
    //非連結だと0だろ
    if(v[s]==0 or v[s]!=v[t]) cout << "no" << endl;
    else cout << "yes" << endl;
  }
  # if 0
  for(int i=0;i<n;i++){cout <<  v[i] << " ";}
  cout << endl;
  # endif
}