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++: #define scanf_s scanf
#include <string>
#include <stdio.h>
#include <math.h>
#include <stack>
#include <queue>
#include <list>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

#define MAX 100
#define _MAX 1000
struct Graph
{
	int id, k = 0;
	list<int> node;
	int d = -1;
};
Graph G[MAX];
list<int> co;
int bo = false;
void Connect(Graph *g,Graph *f)
{
	if (g->k >= 0) {
		int a = true;
		co.push_back(g -> id);
	//	printf("%d,", g->id);
		for (auto i = g->node.begin(); i != g->node.end(); ++i) {
			if (&G[*i] == f) { bo = true; return; }
			for (auto j = co.begin(); j != co.end(); ++j) {
				if (*j == *i) {
					a = false;
					break;
				}
			}
			if(a) Connect(&G[*i], f);
			a = true;
		}
	}
}
int main(void)
{
	int n, m, q, a, b;
	int qq[_MAX] = { 0 };
	scanf_s("%d %d", &n, &m);
	for (int i = 0; i < m; ++i) {
		scanf_s("%d %d", &a, &b);
		G[a].id = a; G[b].id = b;
		++G[a].k; G[a].node.push_back(b);
		++G[b].k; G[b].node.push_back(a);
	}
	scanf_s("%d", &q);
	for (int i = 0; i < q; ++i) {
		scanf_s("%d %d", &a, &b);
		bo = 0;
		Connect(&G[a], &G[b]);
		qq[i] = bo;
		co.clear();
	}
	for (int i = 0; i < q; ++i) {
		if(qq[i]) printf("yes\n");
		else printf("no\n");
	}
}

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<stdio.h>
#include<vector>
#include<string>
#include<iostream>
using namespace std;

vector<vector<int> >g;
int n,m,q,s,t;

vector<bool>visited;
vector<int>color;
void dfs(int s){
    for(int i=0;i<g[s].size();i++){
        if(color[g[s][i]]==-1){
            color[g[s][i]]=color[s];
            dfs(g[s][i]);
        }
    }
}
bool dfs2(int s,int t){
    if(s==t)return true;
    visited[s]=true;
    for(int i=0;i<g[s].size();i++){
        if(!visited[g[s][i]]){
            if(dfs2(g[s][i],t)){
                return true;
            }
        }
    }
    return false;
}
int main() {
    scanf("%d %d",&n,&m);
    g.resize(n);
    color.resize(n,-1);
    for(int i=0;i<m;i++){
        scanf("%d %d",&s,&t);
        g[s].push_back(t);
        g[t].push_back(s);
    }
    for(int i=0;i<n;i++){
        if(color[i]==-1){
            color[i]=i;
            dfs(i);
        }
    }
    scanf("%d",&q);
    for(int i=0;i<q;i++){
        scanf("%d %d",&s,&t);
        visited.resize(n,false);
        string s1=(dfs2(s,t)?"yes":"no");
        string s2=(color[s]==color[t]?"yes":"no");
        if(s1!=s2&&s1=="yes")return 1;
        cout<<s2<<endl;
    }
    return 0;
}