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>
using namespace std;
vector<vector<int>> G(100000);
vector<int> c(100000);
void dfs(int s, int x){
    if(c[s]) return;
    c[s]=x;
    for(auto a:G[s]) dfs(a,x);
}
int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n,m;
    cin>>n>>m;
    for(int i=0;i<m;++i){
        int a,b;
        cin>>a>>b;
        G[a].push_back(b);
        G[b].push_back(a);
    }
    for(int i=0;i<n;++i) dfs(i,i+1);
    int q;
    cin>>q;
    for(int i=0;i<q;++i){
        int a,b;
        cin>>a>>b;
        cout<<(c[a]-c[b]?"no":"yes")<<endl;
    }
}

C++: 
#include<stdio.h>
#include<queue>
#include<algorithm>

#define MAX 100000

int G[MAX+1][MAX+1];
int n, m;
std::queue<int> Q;


bool bfs(int src, int dest) {
    bool C[MAX];
    for (int i = 0; i < n; ++i) C[i] = false;

    Q.push(src);
    while(!Q.empty()) {
        int cur = Q.front();Q.pop();
        for (int i = 0; i < n; ++i) {
            if (G[cur][i] == 0) continue;
            if (C[i]) continue;
            if (i == dest) return true;
            Q.push(i);
            C[i] = true;
        }
    }

    return false;
}

int main() {
    scanf("%d %d", &n, &m);
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            G[i][j] = 0;
        }
    }
    for (int i = 0; i < m; ++i) {
        int u,k;
        scanf("%d %d", &u, &k);
        G[u][k] = 1;
        G[k][u] = 1;
    }

    int q;
    scanf("%d", &q);
    for (int i = 1; i <= q; ++i) {
        int s,d;
        scanf("%d %d", &s, &d);
        bfs(s, d) ? printf("yes\n") : printf("no\n");
    }

}

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

void dfs(vector<vector<int>> &adj_list, vector<int> &colors, int s, int c)
{
    stack<int> st;
    colors[s] = c;
    st.push(s);
    while (!st.empty())
    {
        int u = st.top();
        st.pop();
        for (int i = 0; i < adj_list[u].size(); i++)
        {
            int v = adj_list[u][i];
            // cout << u << ", " << v << endl;
            if (colors[v] == -1)
            {
                // cout << 1 << endl;
                colors[v] = c;
                st.push(v);
            }
        }
    }
}

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

    vector<vector<int>> adj_list(n);
    for (int i = 0; i < m; i++)
    {
        int s, t;
        cin >> s >> t;
        adj_list[s].push_back(t);
        adj_list[t].push_back(s);
    }

    int id = 0;
    vector<int> colors(n, -1);
    for (int i = 0; i < n; i++)
    {
        if (colors[i] == -1)
        {
            dfs(adj_list, colors, i, id++);
        }

        // for (auto a : colors)
        // {
        //     cout << a << ", ";
        // }
        // cout << endl;
    }

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

    return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <string>
#include <numeric>
#include <cstring>
#include <cmath>
#include <stack>

const int MOD = 1e9 + 7;
const int MAX = 100000;
#define rep(i,n) for(int i=0;i<(n);i++)

using ll = long long int;
using namespace std;

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

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] == -1)
            {
                color[v] = c;
                S.push(v);
            }
        }
    }
}

void assignColor()
{
    int id = 1;
    for(int i = 0; i < n; i++)
        color[i] = -1;
    for(int u = 0; u < n; u++)
        if(color[u] == -1)
            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 <array>
#include <vector>
#include <deque>
#include <queue>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <string>
#include <algorithm>
#include <numeric>
#include <functional>
#include <iterator>
#include <tuple>
#include <utility>
#include <limits>
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cstdint>
#include <cassert>

using namespace std;

#define FOR(i, start, end) for(int i = (start); i < (end); ++i)
#define REP(i, n) FOR(i, 0, n)

#define DBG
#undef DBG

constexpr int N_MAX = 100000;

int n, m;
vector<int> graph[N_MAX];
int color[N_MAX];

void dfs(int i, int c)
{
    color[i] = c;

    for(int j : graph[i]) {
        if(color[j]) continue;

        dfs(j, c);
    }
}

void solve()
{
    int c = 1;

    REP(i, n) {
        if(color[i]) continue;

        dfs(i, c);
        ++c;
    }
}

int main()
{
    cin >> n >> m;
#ifdef DBG
    cout << n << " " << m << "\n";
#endif

    REP(_, m) {
        int s, t;
        cin >> s >> t;
        graph[s].push_back(t);
        graph[t].push_back(s);
#ifdef DBG
        cout << s << " " << t << "\n";
#endif
    }

    solve();

    int q;
    cin >> q;
#ifdef DBG
    cout << q << "\n";
#endif

    REP(_, q) {
        int s, t;
        cin >> s >> t;
#ifdef DBG
        cout << s << " " << t << "\n";
#endif
        bool conn = color[s] == color[t];
        cout << (conn ? "yes" : "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;
}