Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N, M := sc.nextInt(), sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < M; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}
	group := make([]int, N)
	for i := 0; i < N; i++ {
		group[i] = -1
	}
	var dfs func(cur int)
	dfs = func(cur int) {
		for i := 0; i < len(G[cur]); i++ {
			next := G[cur][i]
			if group[next] == -1 {
				group[next] = group[cur]
				dfs(next)
			}
		}
	}
	num := 0
	for i := 0; i < N; i++ {
		if group[i] == -1 {
			group[i] = num
			dfs(i)
			num++
		}
	}

	Q := sc.nextInt()
	for i := 0; i < Q; i++ {
		s, t := sc.nextInt(), sc.nextInt()
		if group[s] == group[t] {
			fmt.Fprintln(wtr, "yes")
		} else {
			fmt.Fprintln(wtr, "no")
		}
	}
	wtr.Flush()
}

C++: #include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for(int i = 0; i < (int)n; ++i)
#define FOR(i, a, b) for(int i = a; i < (int)b; ++i)
#define rrep(i, n) for(int i = ((int)n - 1); i >= 0; --i)

typedef long long ll;
typedef long double ld;

const int Inf = 1e9;
const double EPS = 1e-9;
const int MOD = 1e9 + 7;

class UnionFind {
    public:
        vector<int> rank, p, size;

        UnionFind() {}
        UnionFind(int s) {
            rank.resize(s, 0);
            p.resize(s, 0);
            size.resize(s, 0);
            rep (i, s) init(i);
        }

        void init(int x) {
            p[x] = x;
            rank[x] = 0;
            size[x] = 1;
        }

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

        void unite(int x, int y) {
            if (isSame(x, y)) return;
            link(root(x), root(y));
        }

        void link(int x, int y) {
            if (rank[x] > rank[y]) {
                p[y] = x;
                size[x] += size[y];
            } else {
                p[x] = y;
                size[y] += size[x];
                if (rank[x] == rank[y]) {
                    rank[y]++;
                }
            }
        }

        int root(int x) {
            if (x != p[x]) {
                p[x] = root(p[x]);
            }
            return p[x];
        }

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

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(0);
    int n, m, q;
    cin >> n >> m;
    UnionFind uf = UnionFind(n);
    rep (i, m) {
        int s, t;
        cin >> s >> t;
        uf.unite(s, t);
    }
    cin >> q;
    rep (i, q) {
        int s, t;
        cin >> s >> t;
        if (uf.isSame(s, t)) 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 (void) {
  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 <bits/stdc++.h>
using namespace std;

#define NIL -1

void dfs(int r, int id, vector<vector<int>> &G, vector<int> &color) {
    stack<int> S;
    S.push(r);

    color[r] = id;
    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] = id;
                S.push(v);
            }
        }
    }
}

void assignColor(vector<vector<int>> &G, vector<int> &color) {
    int id = 1;

    for (int i = 0; i < G.size(); i++)
        color[i] = NIL;

    for (int u = 0; u < G.size(); u++) {
        if (color[u] == NIL) {
            dfs(u, id, G, color);
            id++;
        }
    }
}

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

    vector<vector<int>> G(n);
    vector<int> color(n);

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

    // グループ分け
    assignColor(G, color);

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

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const ll INF = 1LL << 60;
const ll MOD = 1000000007;

int N, M;
int cnt = 0;
vector<vector<int>> G;

vector<int> seen;
void dfs(int v) {
    seen[v] = cnt;

    for (auto nv : G[v]) {
        if (seen[nv] != -1) continue;

        dfs(nv);
    }
}

int main() {
    cin >> N >> M;
    G.resize(N);
    seen.assign(N, -1);
    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 v = 0; v < N; v++) {
        if (seen[v] != -1) continue;

        dfs(v);
        cnt++;
    }

    int q;  cin >> q;
    for (int i = 0; i < q; i++) {
        int a, b; cin >> a >> b;
        if (seen[a] == seen[b]) {
            cout << "yes" << endl;
        } else {
            cout << "no" << endl;
        }
    }
    return 0;
}