Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	m := getNextInt(scanner)
	nodes := make([]Node, n)

	for i := 0; i < n; i++ {
		nodes[i].list = make([]int, 0)
	}

	for i := 0; i < m; i++ {
		s := getNextInt(scanner)
		t := getNextInt(scanner)
		nodes[s].list = append(nodes[s].list, t)
		nodes[t].list = append(nodes[t].list, s)
	}

	c := 1
	for i := 0; i < n; i++ {
		if nodes[i].c == 0 {
			traverse(nodes, i, c)
			c++
		}
	}

	q := getNextInt(scanner)

	for i := 0; i < q; i++ {
		s := getNextInt(scanner)
		t := getNextInt(scanner)
		if nodes[s].c == nodes[t].c {
			fmt.Fprintln(writer, "yes")
			continue
		}
		fmt.Fprintln(writer, "no")
	}

	writer.Flush()
}

// Node ...
type Node struct {
	list []int
	c    int
}

func traverse(nodes []Node, r, c int) {
	nodes[r].c = c
	for _, i := range nodes[r].list {
		if nodes[i].c != 0 {
			continue
		}
		traverse(nodes, i, c)
	}
}

C++: #ifdef LOCAL
#pragma GCC optimize ("O0")
#else
#pragma GCC optimize ("O3")
#endif


#include <bits/stdc++.h>


using namespace std;

using ll = long long;
const int INF = 1e9 + 7;
const int MOD = INF;
const ll INF_LL = 1e18 + 7;

#define __overload3(_1, _2, _3, name,...) name
#define rep(...) __overload3(__VA_ARGS__, repFromUntil, repUntil, repeat)(__VA_ARGS__)
#define repeat(times) repFromUntil(__name, 0, times)
#define repUntil(name, times) repFromUntil(name, 0, times)
#define repFromUntil(name, from, until) for (int name = from, name##__until = (until); name < name##__until; name++)
#define repFromTo(name, from, to) repFromUntil(name, from, to + 1)
#define repr(...) __overload3(__VA_ARGS__, reprFromUntil, reprUntil, repeat)(__VA_ARGS__)
#define reprUntil(name, times) reprFromUntil(name, 0, times)
#define reprFromUntil(name, from, until) for (int name = until - 1, name##__from = (from); name >= name##__from; name--)
#define reprFromTo(name, from, to) reprFromUntil(name, from, to + 1)

#define debugos OUT
#ifdef LOCAL
#define debug(v) {printf("L%d %s > ",__LINE__,#v);debugos<<(v)<<newl;}
#define debugv(v) {printf("L%d %s > ",__LINE__,#v);for(auto e:(v)){debugos<<e<<" ";}debugos<<newl;}
#define debuga(m,w) {printf("L%d %s > ",__LINE__,#m);for(int x=0;x<(w);x++){debugos<<(m)[x]<<" ";}debugos<<newl;}
#define debugaa(m,h,w) {printf("L%d %s >\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){debugos<<(m)[y][x]<<" ";}debugos<<newl;}}
#else
#define debug(v) {}
#define debugv(v) {}
#define debuga(m,w) {}
#define debugaa(m,h,w) {}
#endif

#define newl "\n"

#define all(iter) begin(iter), end(iter)


template <class T> bool chmin(T& var, T x) {
  if (var > x) {
    var = x;
    return true;
  } else return false;
}
template <class T> bool chmax(T& var, T x) {
  if (var < x) {
    var = x;
    return true;
  } else return false;
}

class MyScanner {
  public:
    template<typename T> void input_integer(T& var) {
        var = 0; T sign = 1;
        int cc = getchar();
        for (; cc<'0' || '9'<cc; cc = getchar())
            if (cc == '-') sign = -1;
        for (; '0' <= cc && cc <= '9'; cc = getchar())
            var = (var << 3) + (var << 1) + cc - '0';
        var = var * sign;
    }
    int c() { char c; while (c = getchar(), c == ' ' or c == '\n'); return c; }
    MyScanner& operator>>(char& var) { var = c(); return *this; }
    MyScanner& operator>>(int& var) { input_integer<int>(var); return *this; }
    MyScanner& operator>>(ll& var) { input_integer<ll>(var); return *this; }
    MyScanner& operator>>(string& var) {
        int cc = getchar();
        for (; !isvisiblechar(cc); cc = getchar());
        for (; isvisiblechar(cc); cc = getchar())
            var.push_back(cc);
        return *this;
    }
    operator int() {
      int n;
      *this >> n;
      return n;
    }
    operator ll() {
      ll n;
      *this >> n;
      return n;
    }
    private:
      int isvisiblechar(int c) {
        return 0x21 <= c && c <= 0x7E;
      }
};
class MyPrinter {
  public:
    template<typename T>
    void output_integer(T var) {
        if (var == 0) { putchar('0'); return; }
        if (var < 0)
            putchar('-'),
            var = -var;
        char stack[32]; int stack_p = 0;
        while (var)
            stack[stack_p++] = '0' + (var % 10),
            var /= 10;
        while (stack_p)
            putchar(stack[--stack_p]);
    }
    MyPrinter& operator<<(char c) { putchar(c); return *this; }
    template <typename T>
    MyPrinter& operator<<(T var) { output_integer<T>(var); return *this; }
    MyPrinter& operator<<(char* str_p) { while (*str_p) putchar(*(str_p++)); return *this; }
    MyPrinter& operator<<(const char* str_p) { while (*str_p) putchar(*(str_p++)); return *this; }
    MyPrinter& operator<<(const string& str) {
        const char* p = str.c_str();
        const char* l = p + str.size();
        while (p < l) putchar(*p++);
        return *this;
    }
    // MyPrinter& operator<<(const modint& var) { output_integer<ll>(var.value); return *this; }
    template <typename T>
    void operator()(T x) {
        *this << x << newl;
    }
};
MyScanner IN;
MyPrinter OUT;

class union_find {
  public:
    /// <param name="len">要素数</param>
    union_find(int len) {
      parents = new int[len];
      depths = new int[len];
      for (int i = 0; i < len; i++) parents[i] = i;
      memset(depths, 0, len);
    }
    /// 根を特定　あまり外部から使わない
    int root(int x) {
      return parents[x] == x ? x :
             root(parents[x]);
    }
    /// 2つの要素が同じ木に属すると宣言
    void unite(int x, int y) {
      x = root(x);
      y = root(y);
      if (x == y) return;
      if (depths[x] < depths[y]) parents[x] = y;
      else {
        parents[y] = x;
        if (depths[x] == depths[y]) depths[x]++;
      }
    }
    /// 同じ木に属するか
    bool same(int x, int y) {
      return root(x) == root(y);
    }
  private:
    int *parents;
    int *depths;
};

int main() {
  int n = IN, m = IN;
  union_find uf(n);
  rep(m) {
    uf.unite(IN, IN);
  }
  int q = IN;
  rep(q) OUT(uf.same(IN, IN) ? "yes" : "no");
}

C++: #include <iostream>
#include <vector>
const int MAX_N = 100000;
const int NIL = -1;
using namespace std;

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

void dfs(int u, int col) {
    color[u] = col;
    for (auto i = 0; i < G[u].size(); i++) {
        int v = G[u][i];
        if (color[v] == NIL) {
            color[v] = col;
            dfs(v, col);
        }
    }
}

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

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

    dfs_init();

    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;
        }
    }

    return 0;
}