Go: package main

import (
	"fmt"
)

var n, m int
var g [][]int
var color []int

func main() {
	fmt.Scan(&n, &m)
	g = make([][]int, n) // SNSの関係を表すグラフ
	for i := 0; i < m; i++ {
		var a, b int
		fmt.Scan(&a, &b)
		g[a] = append(g[a], b) // 無向重みなしグラフ
		g[b] = append(g[b], a)
	}
	color = make([]int, n) // 各ノードにつける色
	for i := 0; i < len(color); i++ {
		color[i] = -1 // 初期化しておく
	}
	type query struct {
		s, t int
	}
	var Q int
	fmt.Scan(&Q)
	qs := make([]query, Q)
	for i := 0; i < Q; i++ {
		fmt.Scan(&qs[i].s, &qs[i].t)
	}
	// fmt.Println("n", n, "m", m, "g", g, "Q", Q, "qs", qs)
	// 全ての頂点からdfsする
	id := 1
	for u := 0; u < n; u++ {
		if color[u] == -1 {
			dfs(u, id)
			id++
		}
	}
	// fmt.Println("color", color)
	for i := 0; i < Q; i++ {
		if color[qs[i].s] == color[qs[i].t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func dfs(v, c int) {
	// fmt.Printf("dfs(v %d, c %d) en:\n", v, c)
	color[v] = c
	for _, vv := range g[v] {
		// fmt.Printf("  v %d, g[v] %v, vv %d\n", v, g[v], vv)
		if color[vv] == -1 {
			dfs(vv, c)
		}
	}
}

C++: #include <iostream>
using namespace std;
 
int main() {
int d[100100];
int m,n,q;
cin>>n>>m;
for(int i=0;i<n;i++){
    d[i]=i;
}
for(int l=0;l<m;l++){
    int a,b;
    cin>>a>>b;
    int j ,h;
    j=a,h=b;
while(d[j]!=j )
    j=d[j];
}
while(d[h]!=h )
    h=d[h];
}
if(j!=h){
    d[j]=h;
    d[a]=h;
    d[b]=h;
}
}
cin>>q;
for(int y=0;y<q;y++){
    int a,b;
    cin>>a>>b;
        int j ,h;
    j=a,h=b;
while(d[j]!=j )
    j=d[j];
}
while(d[h]!=h )
    h=d[h];
}
    if(j==h){
        cout<<"yes"<<endl;
    }
    else{
        cout<<"no"<<endl;
    }
}
    return 0;
}

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

using namespace std;
static const int MAX=100000;
static const int NIL=-1;

int n;
vector<int> G[MAX];
int color[MAX];

void dfs(int r,int c){
  stack<int> S;
  S.push(r);
  color[r]=c;
  while(!S.empty()){
    int u=S.top();
    S.pop();
    for(int i=0;i<G[u].size();i++){
      int v=G[u][i];
      if(color[v]==NIL){
	color[v]=c;
	S.push(v);
      }
    }
  }
}

void assignColor(){
  int id=1;
  for(int i=0;i<n;i++)
       color[i]=NIL;
  for(int u=0;u<n;u++){
    if(color[u]==NIL)
          dfs(u,id++);
  }
}

int main(){
  int s,t,m,q;

  cin>>n>>m;

  for(int i=0;i<m;i++){
    cin>>s>>t;
    G[s].push_back(t);
    G[t].push_back(s);
  }
  assignColor();

  cin>>q;

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

C++: /* 
 * ALDS1_11B.cpp
 */
#include <iostream>
#include <queue>
#include <cstdio>
#include <cstdlib>
#include <cstring>

using namespace std;

using Friends = vector<int>;
using SNS = vector<Friends>;

int n, m, q;
bool visited[100000];
SNS sns;

int main(void) {

    scanf("%d %d", &n, &m);
    sns.resize(n);
    for (int i = 0, id, f; i < m; ++i) {
        scanf("%d %d", &id, &f);
        sns[id].push_back(f);
        sns[f].push_back(id);
    }

    scanf("%d", &q);
    for (int i = 0, id, f; i < q; ++i) {
        scanf("%d %d", &id, &f);
        memset(visited, 0, sizeof(bool)*n);
        queue<int> q;
        q.push(id);
        bool found = false;
        while (!q.empty()) {
            int per = q.front();
            q.pop();
            if (visited[per])
                continue;
            if (per == f) {
                found = true;
                break;
            }
            visited[per] = true;
            for (int j = 0; j < sns[per].size(); ++j) {
                q.push(sns[per][j]);
            }
        }
        if (found)
            printf("yes\n");
        else
            printf("no\n");
    }

    return 0;
}

C++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;
static const int MAX = 100000;
static const int NIL = -1;
int n;
vector<int> G[MAX];
int color[MAX];

void dfs(int r, int c) {
    stack<int> S;
    S.push(r);
    color[r] = c;
    while ( !S.empty() ) {
        int u = S.top();
        S.pop();
        for ( int i = 0; i < G[u].size(); i++ ){
            int v = G[u][i];
            if ( color[v] == NIL ) {
                color[v] = c; S.push(v);
            }
            
        }
    }
        }

void assignColor() { int id = 1;
    for(int i=0; i<n; i++) color[i]=NIL;
    for(int u=0; u<n; u++){
        if(color[u] ==NIL) dfs(u,id++);
    }
    }

int main() {
    int s, t, m, q;
    cin >> n >> m;

    for ( int i = 0; i<m; i++){
         cin >> s >> t;
        G[s].push_back(t);
        G[t].push_back(s);
         }
    assignColor();
    cin >> q;
    
         for ( int i = 0; i < q; i++ ) {
             cin >> s >> t;
             if ( color[s] == color[t] ) {
                 cout << "yes" << endl;
                 
             } else {
                     cout << "no" << endl;
                 
             }
         }
         return 0; }

C++: #include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#define Lens 100005

using namespace std;
int n, m, q;
vector<int> A[Lens];
queue<int>	Q;

int Find(int s, int t)
{
	Q.push(s);
	while (!Q.empty())
	{
		s = Q.front();
		Q.pop();
		for (int j = 0; j < A[s].size(); j++)
		{
			Q.push(A[s][j]);
			if (A[s][j] == t)
			{
				return 1;
			}
		}
	}
	return 0;
}

int main()
{
	cin >> n >> m;
	for (int i = 0; i < m; i++)
	{
		int s, t;
		cin >> s >> t;
		A[s].push_back(t);
	}
	cin >> q;
	for (int i = 0; i < q; i++)
	{
		int flag = 0;
		int s, t;
		cin >> s >> t;
		if (Find(s, t))
			cout << "yes" << endl;
		else if (Find(t, s))
			cout << "yes" << endl;
		else
			cout << "no" << endl;
	}
	return 0;
}