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<cstdio>
#include<queue>
#include<vector>
#define N_MAX 100005
using namespace std;
struct Node{
    vector<int> vct;
    char type;
    char state;//0:undiscovered
};
vector<Node> nodes;
int n;
void bfs(){
    queue<int> Q;
    char type=1;
    for(int i=0;i<n;i++){
        if(nodes[i].state==0){
            Q.push(i);
            nodes[i].type = type;
            nodes[i].state = 1;
            while(!Q.empty()){
                int active = Q.front();
                int total = nodes[active].vct.size();
                for(int i=0;i<total;i++){
                    int newIndex=nodes[active].vct[i];
                    if(nodes[newIndex].state==0){
                        Q.push(newIndex);
                        //printf("== %d -> %d ==\n", active, newIndex);
                        nodes[newIndex].type = type;
                        nodes[newIndex].state = 1;
                    }
                }
                Q.pop();
            }
            type++;
        }
    }
}
int main(){
    int rel;
    scanf("%d%d", &n, &rel);
    for(int i=0;i<n;i++){//initial
        Node init;
        init.type=0;
        init.state=0;
        nodes.push_back(init);
        //printf("initial info: %d %d\n", init.type, init.state);
    }
    for(int i=0;i<rel;i++){
        int maj, sub;
        scanf("%d%d", &maj, &sub);
        nodes[maj].vct.push_back(sub);
        nodes[sub].vct.push_back(maj);//Undirected
    }
    bfs();
    short ques;
    scanf("%d", &ques);
    for(short i=0;i<ques;i++){
        int maj, sub;
        scanf("%d%d", &maj, &sub);
        if(nodes[maj].type==nodes[sub].type){
            printf("yes\n");
        }else{
            printf("no\n");
        }
    }

    /*printf("\n============ now testing ================\n");
    for(int i=0;i<n;i++){
        printf("\t-- %d: type:%d state:%d --\n", i, nodes[i].type, nodes[i].state);
    }*/
    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;
    int i, u, v;
    while ( !S.empty() ) {
        u = S.top();
        S.pop();
        for ( i = 0; i < G[u].size(); i++ ) {
            v = G[u][i];
            if ( color[v] == NIL ) {
                color[v] = c;
                S.push(v);
            }
        }
    }
}
  
void assignColor() {
    int id = 0;
    int i, u;
    for ( i = 0; i < n; i++ ) color[i] = NIL;
    for ( u = 0; u < n; u++ ) {
        if ( color[u] == NIL ) dfs(u, id++);
    }
}
  
int main() {
    int s, t, m, q, i;
  
    cin >> n >> m;
  
    for ( i = 0; i < m; i++ ) {
        cin >> s >> t;
        G[s].push_back(t);
        G[t].push_back(s);
    }
  
    assignColor();
  
    cin >> q;
  
    for ( 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;
}

C++: #include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#define Lens 100005

using namespace std;
int n, m, q;
vector<int> A[Lens];
queue<int>	Q;
char c[Lens], d[Lens];

int Find(int s, int t)
{
	Q.push(s);
	c[s] = 'g';
	while (!Q.empty())
	{
		s = Q.front();
		Q.pop();
		c[s] = 'g';
		for (int j = 0; j < A[s].size(); j++)
		{
			if (c[A[s][j]] == 'w')
				Q.push(A[s][j]);
			if (A[s][j] == t)
			{
				return 1;
			}
		}
	}
return 0;
}

int main()
{
	cin >> n >> m;
	for (int i = 0; i < m; i++)
	{
		int s, t;
		cin >> s >> t;
		d[s] = d[t] = 'w';
		A[s].push_back(t);
		A[t].push_back(s);
	}
	cin >> q;
	for (int i = 0; i < q; i++)
	{
		for (int j = 0; j < n; j++)
			c[j] = d[j];
		int s, t;
		cin >> s >> t;
		if (Find(s, t))
			cout << "yes" << endl;

		else
			cout << "no" << endl;
	}
	return 0;
}

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;
    }
}