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>
#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;
char c[Lens], d[Lens];

int Find(int s, int t)
{
	Q.push(s);
	c[s] = 'g';
	while (!Q.empty())
	{
		s = Q.front();
		Q.pop();
		c[s] = 'g';
		for (int j = 0; j < A[s].size(); j++)
		{
			if (c[A[s][j]] == 'w')
				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;
		d[s] = d[t] = 'w';
		A[s].push_back(t);
		A[t].push_back(s);
	}
	cin >> q;
	for (int i = 0; i < q; i++)
	{
		for (int j = 0; j < n; j++)
			c[j] = d[j];
		int s, t;
		cin >> s >> t;
		if (Find(s, t))
			cout << "yes" << endl;

		else
			cout << "no" << endl;
	}
	return 0;
}

C++: #include<vector>

class UnionFind {
public:
    UnionFind(int N) :parent(N), rank(N, 0), size(N, 1) {
        for (int i = 0; i < N; ++i) parent[i] = i;
    }
    int find(int x) {
        return x == parent[x] ? x : parent[x] = find(parent[x]);
    }
    bool same(int x, int y) {
        return find(x) == find(y);
    }
    void unite(int x, int y) {
        x = find(x), y = find(y);
        if (x == y) return;
        if (rank[x] < rank[y]) parent[x] = y;
        else {
            parent[y] = x;
            if (rank[x] == rank[y]) rank[x]++;
            std::swap(x, y);
        }
        size[y] += size[x];
        size[x] = 0;
    }
    int getParentRank(int x) {
        return rank[find(x)];
    }
    int getParentSize(int x) {
        return size[find(x)];
    }
    int getSize(int x) {
        return size[x];
    }
private:
    std::vector<int> parent, rank, size;
};
#include<iostream>
using namespace std;
int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n,m;
    cin>>n>>m;
    UnionFind UF(n);
    for(int i=0;i<m;++i){
        int a,b;
        cin>>a>>b;
        UF.unite(a,b);
    }
    int q;
    cin>>q;
    for(int i=0;i<q;++i){
        int a,b;
        cin>>a>>b;
        cout<<(UF.same(a,b)?"yes":"no")<<endl;
    }
}

C++: #include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define loop(i,a,b) for(i=a;i<b;i++)
#define rloop(i,a,b) for(i=a;i>=b;i--)
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
const int inf=1000000001;
const ll INF=1e16;
#define MOD 1000000007
#define mod 1000000009
#define pi 3.14159265358979323846
static const int WHITE=0;
static const int GRAY=1;
static const int BLACK=2;
static const int N=100000;

int n;
vii v(N,vi());
vi color(N),nt(N);

bool dfs(int,int);
int next(int);

int main(){
	int m,i,j;
	cin>>n>>m;
	int s,t;
	loop(i,0,m){
		cin>>s>>t;
		v[s].push_back(t);
		v[t].push_back(s);
	}
	int q;
	cin>>q;
	loop(i,0,q){
		cin>>s>>t;
		bool flag=dfs(s,t);
		if(flag==true){
			cout<<"yes"<<endl;
		}else{
			cout<<"no"<<endl;
		}
	}
}

bool dfs(int s,int t){
	if(s==t){
		return true;
	}
	int i;
	loop(i,0,n+1){
		color[i]=WHITE;
	}
	stack<int> st;
	st.push(s);
	color[s]=GRAY;
	while(!st.empty()){
		int u=st.top();
		int u2=next(u);
		if(u2==t){
			return true;
		}else if(u2!=-1){
			color[u2]=GRAY;
			st.push(u2);
		}else{
			color[u]=BLACK;
			st.pop();
		}
	}
	return false;
}

int next(int u){
	int i;
	loop(i,0,v[u].size()){
		if(color[v[u][i]]==WHITE){
			return v[u][i];
		}
	}
	return -1;
}

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<vector>
#include<stack>
using namespace std;
#define max 100000
#define 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;
}