Go: package main

import (
	"bufio"
	"container/list"
	"os"
	"strconv"
	"fmt"
)

const (
	MAX = 100000
	NIL = -1
)

var (
	n     int
	G     [MAX][]int
	color [MAX]int
)

func DFS(r int, c int) {
	S := list.New()
	S.PushFront(r)
	color[r] = c
	for S.Len() != 0 {
		u := S.Remove(S.Front()).(int)
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == NIL {
				color[v] = c
				S.PushFront(v)
			}
		}
	}
}

func assignColor() {
	id := 1
	for i := 0; i < n; i++ {
		color[i] = NIL
	}
	for i := 0; i < n; i++ {
		if color[i] == NIL {
			id++
			DFS(i, id)
		}
	}
}

func main() {
	var s, t, m, q int
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	scanner.Scan()
	n, _ = strconv.Atoi(scanner.Text())
	scanner.Scan()
	m, _ = strconv.Atoi(scanner.Text())
	for i := 0; i < m; i++ {
		scanner.Scan()
		s, _ = strconv.Atoi(scanner.Text())
		scanner.Scan()
		t, _ = strconv.Atoi(scanner.Text())
		if i == 0 {
			G[s] = make([]int, 0)
			G[t] = make([]int, 0)
		}
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)
	}

	assignColor()
	scanner.Scan()
	q, _ = strconv.Atoi(scanner.Text())
	for i := 0; i < q; i++ {
		scanner.Scan()
		s, _ = strconv.Atoi(scanner.Text())
		scanner.Scan()
		t, _ = strconv.Atoi(scanner.Text())
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

C++: #include <iostream>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>
#define N 100000
using namespace std;

int color[N];
vector<int> G[N];
queue<int> Q;
int n;

void bfs(int s,int c) {
	Q.push(s);
	color[s] = c;
	while (!Q.empty()) {
		for (unsigned int it = 0;it < G[Q.front()].size();it++)
			if (color[G[Q.front()][it]] == 0){
				Q.push(G[Q.front()][it]);
				color[G[Q.front()][it]] = c;
		    }
		Q.pop();
	 }
}

void Color() {
	int c = 1;
	for(int i=0;i<n;i++)
		if (color[i] == 0) { bfs(i, c); c++; }
}

int main() {
	int m, q;
	cin >> n >> m;
	for (int i = 0;i < m;i++) {
		int u, v;
		cin >> u >> v;
		G[u].push_back(v);
		G[v].push_back(u);
	}

	Color();

	cin >> q;
	for (int i = 0;i < q;i++) {
		int u, v;
		cin >> u >> v;
		if (color[u] == color[v] && color[u] != 0)
			cout << "yes" << endl;
		else
			cout << "no"<<endl;
	}
}

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

using namespace std;


vector<int> vertexes[100000];
stack<int> visiting;
bool discovered[100000];
int belong[100000];
int subgraph_id = 0;


void dfs(int v)
{
    visiting.push(v);
    discovered[v] = true;
    belong[v] = ++subgraph_id;

    while (!visiting.empty()) {
        int now = visiting.top();
        visiting.pop();


        for (vector<int>::iterator it = vertexes[now].begin(); it != vertexes[now].end(); it++) {
            if (!discovered[*it]) {
                discovered[*it] = true;
                belong[*it] = subgraph_id;
                visiting.push(*it);
            }
        }
    }
}


int main()
{
    int n, m;
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int x, y;
        cin >> x >> y;
        vertexes[x].push_back(y);
        vertexes[y].push_back(x);
    }

    for (int i = 0; i < n; i++)
        if (!discovered[i])
            dfs(i);

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

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

using namespace std;

#define ll long long
typedef complex<double> P;

int main() {
  int n, m; cin >> n >> m;
  int adj[n][n] = {};

  for (int i = 0; i < m; i++) {
    int v, u; cin >> v >> u;
    adj[v][u] = adj[u][v] = 1;
  }

  int q; cin >> q;
  int sd[n] = {};

  for (int i = 0; i < q; i++) {
    int s, t; cin >> s >> t;
    fill(sd, sd+n, 0);

    queue<int> que;
    que.push(s);
    bool f = false;

    while(!que.empty()) {
      int v = que.front(); que.pop();
      if(v == t) {
        f = true;
        break;
      }

      for (int j = 0; j < n; j++) {
        if(adj[v][j] == 1 && sd[j] == 0) {
          que.push(j);
        }
      }
    }

    cout << (f ? "yes" : "no") << endl;

  }
}

C++: #include <map>
#include <set>
#include <list>
#include <cmath>
#include <deque>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <numeric>
#include <utility>
#include <iostream>
#include <algorithm>
#include <functional>
#include <unordered_map>
#include <unordered_set>

using namespace std;

#define ll long long
#define ull unsigned long long
#define INF (1 << 30)
#define LLINF (1LL << 62)
#define MOD7 1000000007
#define MOD9 1000000009
#define eps 1e-9
#define P pair<int, int>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pul pair<ull, ull>
#define all(a) (a).begin(), (a).end()
#define FOR(i,a,b) for (int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);--i)
#define REP(i,n) for (int i=0;i<(n);++i)
#define RREP(i,n) for (int i=(n)-1;i>=0;--i)

void YES() { cout << "YES" << endl; }
void NO() { cout << "NO" << endl; }
void Yes() { cout << "Yes" << endl; }
void No() { cout << "No" << endl; }
void yes() { cout << "yes" << endl; }
void no() { cout << "no" << endl; }

template<class T>
class DirectedGraph {
public:
	class Edge {
	public:
		int to;
		T cost;

		Edge(int t, T c) : to(t), cost(c) {}

		bool operator<(const Edge& right) const {
			return cost == right.cost ? to < right.to : cost < right.cost;
		}
	};

	vector<vector<Edge>> G;
	int V;

	DirectedGraph(int n = 0) {
		resize(n);
	}

	void resize(int n) {
		V = n;
		G.resize(n);
	}

	void addEdge(int from, int to, T cost = 0) {
		int v = max(from, to);
		if (v >= V)
			resize(v + 1);
		G[from].push_back(Edge(to, cost));
	}

	int col = 0;
	vector<int> visit;
	void dfs(int s) {
		//vector<int> visit(V);
		visit.resize(V);
		col++;
		calcDfs(visit, s);
	}

	void calcDfs(vector<int>& visit, int s) {
		if (visit[s])
			return;

		visit[s] = col;
		for (int i = 0; i < G[s].size(); ++i) {
			calcDfs(visit, G[s][i].to);
		}
	}

	vector<int> bfs(int s) {
		vector<int> dist(V);
		queue<int> que;

		fill(dist.begin(), dist.end(), -1);
		dist[s] = 0;
		que.push(s);
		while (!que.empty()) {
			int from = que.front();
			que.pop();
			for (int i = 0; i < G[from].size(); ++i) {
				int to = G[from][i].to;
				if (dist[to] != -1)
					continue;
				dist[to] = dist[from] + 1;
				que.push(to);
			}
		}

		return dist;
	}
};

int main() {
	DirectedGraph<int> g;
	int n, m, from, to;
	cin >> n >> m;
	while (m--) {
		cin >> from >> to;
		g.addEdge(from, to);
	}
	
	for (int i = 0; i < n; ++i)
		g.dfs(i);

	int q;
	cin >> q;
	while (q--) {
		cin >> from >> to;
		if (g.visit[from] == g.visit[to])
			yes();
		else
			no();
	}

	return 0;
}