Go: package main

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

// Node 頂点
type Node struct {
	gid  int   // グループID
	edge []int // 隣接辺
}

// NoID グループIDなし
const NoID = -1

// NewNode 頂点の生成
func NewNode() *Node {
	return &Node{gid: NoID, edge: []int{}}
}

func parseNode(nodes []*Node, gid int, queue []int) {
	if len(queue) == 0 {
		return
	}
	var nextQ []int
	for _, id := range queue {
		node := nodes[id]
		if node.gid == NoID {
			node.gid = gid
			for _, edge := range node.edge {
				nextQ = append(nextQ, edge)
			}
		}
	}
	parseNode(nodes, gid, nextQ)
	return
}
func digNode(nodes []*Node, id, gid int) {
	node := nodes[id]
	if node.gid != NoID {
		// 探索済み
		return
	}
	node.gid = gid
	for _, edge := range node.edge {
		digNode(nodes, edge, gid)
	}
	return
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	n, m := eGetInt2(scanner)

	nodes := make([]*Node, n)
	for i := 0; i < n; i++ {
		nodes[i] = NewNode()
	}

	for i := 0; i < m; i++ {
		a, b := eGetInt2(scanner)
		nodes[a].edge = append(nodes[a].edge, b)
		nodes[b].edge = append(nodes[b].edge, a)
	}

	for i := 0; i < n; i++ {
		// 幅優先探索
		// gid := i
		// queue := []int{i}
		// parseNode(nodes, gid, queue)

		// 深さ優先探索
		digNode(nodes, i, i)
	}

	q := eGetInt(scanner)
	for i := 0; i < q; i++ {
		a, b := eGetInt2(scanner)
		if nodes[a].gid == nodes[b].gid {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func eGetInt(scanner *bufio.Scanner) int {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0]
}
func eGetInt2(scanner *bufio.Scanner) (int, int) {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0], t[1]
}

func eGetline(p *bufio.Scanner) string {
	if !p.Scan() {
		if err := p.Err(); err != nil {
			log.Fatal(err.Error())
		}
		return ""
	}
	return p.Text()
}

func eAtoi(s []string) []int {
	ints := make([]int, len(s))
	var err error
	for i, e := range s {
		ints[i], err = strconv.Atoi(e)
		if err != nil {
			log.Fatal(err.Error())
		}
	}
	return ints
}

C++: #include<vector>

class UnionFind {
public:
    UnionFind(int N) :parent(N), rank(N, 0), size(N, 1) {
        for (int i = 0; i < N; ++i) parent[i] = i;
    }
    int find(int x) {
        return x == parent[x] ? x : parent[x] = find(parent[x]);
    }
    bool same(int x, int y) {
        return find(x) == find(y);
    }
    void unite(int x, int y) {
        x = find(x), y = find(y);
        if (x == y) return;
        if (rank[x] < rank[y]) parent[x] = y;
        else {
            parent[y] = x;
            if (rank[x] == rank[y]) rank[x]++;
            std::swap(x, y);
        }
        size[y] += size[x];
        size[x] = 0;
    }
    int getParentRank(int x) {
        return rank[find(x)];
    }
    int getParentSize(int x) {
        return size[find(x)];
    }
    int getSize(int x) {
        return size[x];
    }
private:
    std::vector<int> parent, rank, size;
};
#include<iostream>
using namespace std;
int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n,m;
    cin>>n>>m;
    UnionFind UF(n);
    for(int i=0;i<m;++i){
        int a,b;
        cin>>a>>b;
        UF.unite(a,b);
    }
    int q;
    cin>>q;
    for(int i=0;i<q;++i){
        int a,b;
        cin>>a>>b;
        cout<<(UF.same(a,b)?"yes":"no")<<endl;
    }
}

C++: #include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define loop(i,a,b) for(i=a;i<b;i++)
#define rloop(i,a,b) for(i=a;i>=b;i--)
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
const int inf=1000000001;
const ll INF=1e16;
#define MOD 1000000007
#define mod 1000000009
#define pi 3.14159265358979323846
static const int WHITE=0;
static const int GRAY=1;
static const int BLACK=2;
static const int N=100000;

int n;
vii v(N,vi());
vi color(N),nt(N);

bool dfs(int,int);
int next(int);

int main(){
	int m,i,j;
	cin>>n>>m;
	int s,t;
	loop(i,0,m){
		cin>>s>>t;
		v[s].push_back(t);
		v[t].push_back(s);
	}
	int q;
	cin>>q;
	loop(i,0,q){
		cin>>s>>t;
		bool flag=dfs(s,t);
		if(flag==true){
			cout<<"yes"<<endl;
		}else{
			cout<<"no"<<endl;
		}
	}
}

bool dfs(int s,int t){
	if(s==t){
		return true;
	}
	int i;
	loop(i,0,n+1){
		color[i]=WHITE;
	}
	stack<int> st;
	st.push(s);
	color[s]=GRAY;
	while(!st.empty()){
		int u=st.top();
		int u2=next(u);
		if(u2==t){
			return true;
		}else if(u2!=-1){
			color[u2]=GRAY;
			st.push(u2);
		}else{
			color[u]=BLACK;
			st.pop();
		}
	}
	return false;
}

int next(int u){
	int i;
	loop(i,0,v[u].size()){
		if(color[v[u][i]]==WHITE){
			return v[u][i];
		}
	}
	return -1;
}

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<iostream>
#include<vector>
#include<stack>
using namespace std;
#define max 100000
#define 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<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;
}