Go: package main

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

func main() {
	var n,m int
	fmt.Scan(&n)
	group := make([]int, n)
	g := make([][]int, n)
	for i := 0; i < n; i++ {
		g[i] = []int{}
		group[i] = -1
	}
	
	fmt.Scan(&m)
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	for i := 0; i < m; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())
		
		g[s] = append(g[s], t)
		g[t] = append(g[t], s)
	}
	for i := 0; i < n; i++ {
		if group[i] != -1 {
			continue
		}
		q := []int{i}
		for len(q) > 0 {
			pop := q[0]
			if len(q) > 1 {
				q = q[1:]
			} else {
				q = []int{}
			}
			if group[pop] == -1 {
				q = append(q, g[pop]...)
				group[pop] = i
			}
		}
	}
	sc.Scan()
	q, _ := strconv.Atoi(sc.Text())
	for i := 0; i < q; i++ {
		sc.Scan()
		s, _ := strconv.Atoi(sc.Text())
		sc.Scan()
		t, _ := strconv.Atoi(sc.Text())

		if group[s] == group[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func root(i int, group *[]int) int {
	if i == (*group)[i] {
		return i
	}
	(*group)[i] = root((*group)[i], group)
	return (*group)[i]
}

C++: #include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i,n) for (int i=0;i<(int)(n);i++)
#define codefor int test;scanf("%d",&test);while(test--)
#define INT(...) int __VA_ARGS__;in(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;in(__VA_ARGS__)
#define yn(ans) if(ans)printf("Yes\n");else printf("No\n")
#define YN(ans) if(ans)printf("YES\n");else printf("NO\n")
#define vector2d(type,name,h,...) vector<vector<type>>name(h,vector<type>(__VA_ARGS__))
#define umap unordered_map
#define uset unordered_set
using namespace std;
using ll = long long;
const int MOD=1000000007;
//入力系
void scan(int& a){scanf("%d",&a);}
void scan(long long& a){scanf("%lld",&a);}
template<class T> void scan(T& a){cin>>a;}
template<class T> void scan(vector<T>& vec){for(auto&& it:vec)scan(it);}
void in(){}
template <class Head, class... Tail> void in(Head& head, Tail&... tail){scan(head);in(tail...);}
//出力系
void print(const int& a){printf("%d",a);}
void print(const long long& a){printf("%lld",a);}
void print(const double& a){printf("%.15lf",a);}
template<class T> void print(const T& a){cout<<a;}
template<class T> void print(const vector<T>& vec){if(vec.empty())return;print(vec[0]);for(auto it=vec.begin();++it!= vec.end();){putchar(' ');print(*it);}}
void out(){putchar('\n');}
template<class T> void out(const T& t){print(t);putchar('\n');}
template <class Head, class... Tail> void out(const Head& head,const Tail&... tail){print(head);putchar(' ');out(tail...);}
//デバッグ系
template<class T> void dprint(const T& a){cerr<<a;}
template<class T> void dprint(const vector<T>& vec){if(vec.empty())return;cerr<<vec[0];for(auto it=vec.begin();++it!= vec.end();){cerr<<" "<<*it;}}
void debug(){cerr<<endl;}
template<class T> void debug(const T& t){dprint(t);cerr<<endl;}
template <class Head, class... Tail> void debug(const Head& head, const Tail&... tail){dprint(head);cerr<<" ";debug(tail...);}

int main(){
    INT(n,m);
    int x,y;
    vector<vector<int>> graph(n);
    rep(i,m){
        in(x,y);
        graph[x].push_back(y);
        graph[y].push_back(x); 
    }
    vector<int> color(n,-1);
    int id=0,a;
    rep(i,n){
        if(color[i]==-1){
            id++;
            queue<int> next;
            next.push(i);
            color[i]=id;
            while(!next.empty()){
                a=next.front();
                next.pop();
                rep(j,graph[a].size()){
                    if(color[graph[a][j]]==-1){
                        color[graph[a][j]]=id;
                        next.push(graph[a][j]);
                    }
                }
            }
        }
    }
    codefor{
        in(x,y);
        if(color[x]==color[y])printf("yes\n");
        else printf("no\n");
    }
}

C++: #include <bits/stdc++.h>
using namespace std;

int n, m, q, x, y;
int connect[100001];
vector<int> g[100001];

void dfs(int v, int c) {
    connect[v] = c;
    
    int size_ = g[v].size();
    for (int i = 0; i < size_; ++i) {
        if (connect[g[v][i]] == 0) {
            dfs(g[v][i], c);
        }
    }
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

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

    int c = 1;
    for (int i = 0; i < n; ++i) {
        if (connect[i] == 0) {
            dfs(i, c);
            c++;
        }
    }

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

    return 0;
}

C++: #include <algorithm>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>

using namespace std;

typedef long long ll;

#define MOD 1000000007

vector<int> g[100000];
vector<bool> visit(100000);
vector<int> col(100000);
int c = 1;

void dfs(int v) {
  col[v] = c;
  visit[v] = true;
  for (auto u : g[v]) {
    if (!visit[u]) {
      dfs(u);
    }
  }
}

int main() {
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < m; ++i) {
    int s, t;
    cin >> s >> t;
    g[s].push_back(t);
    g[t].push_back(s);
  }
  for (int i = 0; i < n; ++i) {
    if (!visit[i]) {
      dfs(i);
      c++;
    }
  }
  int q;
  cin >> q;
  for (int i = 0; i < q; ++i) {
    int s, t;
    cin >> s >> t;
    cout << (col[s] == col[t] ? "yes" : "no") << endl;
  }
  return 0;
}

C++: #include <iostream>

using namespace std;

const int N = 100000;
int A[N][N] = {{0}};
int n;

bool dfs(int s, int t) {
    if (A[s][t] == 1) {
        return true;
    }
    for (int i = 0; i < n; ++i) {
        if (i != t && A[s][i] != 0) {
            if (dfs(i, t)) {
                return true;
            }
        }
    }
    return false;
}

int main() {
    int m;
    cin >> n >> m;
    for (int i = 0; i < m; ++i) {
        int s, t;
        cin >> s >> t;
        A[s][t] = 1;
    }

    int q;
    cin >> q;
    for (int j = 0; j < q; ++j) {
        int x, y;
        cin >> x >> y;

        if (dfs(x, y)) {
            cout << "yes";
        } else {
            cout << "no";
        }
        cout << endl;
    }

    return 0;
}

C++: #include<stdio.h>

#define UNION_FIND_MAX_N (100010)
int union_find_par[UNION_FIND_MAX_N];
int union_find_rank[UNION_FIND_MAX_N];

void init(int n)
{
  int i;
  for(i=0;i<n;i++)
    {
      union_find_par[i]=i;
      union_find_rank[i]=0;
    }
}

int find(int x)
{
  if(union_find_par[x]==x)
    return x;
  else
    return union_find_par[x]=find(union_find_par[x]);
}

void unite(int x,int y)
{
  x=find(x);
  y=find(y);
  if(x==y)
    return;
  if(union_find_rank[x]<union_find_rank[y])
    union_find_par[x]=y;
  else
    union_find_par[y]=x;
  if(union_find_rank[x]==union_find_rank[y])
    union_find_rank[x]++;
}

int same(int x,int y)
{
  return find(x)==find(y);
}

int main()
{
  int n,m;
  int i;
  int a,b;
  int q;
  int s,t;
  scanf("%d %d",&n,&m);
  init(n);
  for(i=0;i<m;i++)
    {
      scanf("%d %d",&a,&b);
      unite(a,b);
    }
  scanf("%d",&q);
  for(i=0;i<q;i++)
    {
      scanf("%d %d",&s,&t);
      same(s,t)?puts("yes"):puts("no");
    }
  
  return 0;
}