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
}

Python: # -*- coding: utf-8 -*-
from collections import deque


if __name__ == '__main__':

    n, m = [int(s) for s in input().split(" ")]
    M = [set() for j in range(n)]
    for _ in range(m):
        u, v = [int(s) for s in input().split(" ")]
        M[u].add(v)
        M[v].add(u)
        
    color = [0] * n
    def dfs(u, c):  # depth-first search
        color[u] = c
        for v in M[u]:
            if color[v] == 0:
                dfs(v, c)
    
    c = 1
    for u in range(n):
        if color[u] == 0:
            dfs(u, c)
            c += 1
    
    l = int(input())
    for _ in range(l):
        p, q = [int(s) for s in input().split(" ")]
        if color[p] == color[q]:
            print("yes")
        else:
            print("no")

Python: def DFS(s, j):
    group[s] = j
    for i in range(n):
        if i in G[s] and group[i] == 0:
            DFS(i, j)

n, m = map(int, input().split())
G = [[] for j in range(n)]

for i in range(m):
    s, t = map(int, input().split())
    G[s].append(t)
    G[t].append(s)

group = [0 for i in range(n)]
j = 1
for i in range(n):
    if group[i] == 0:
        DFS(i, j)
        j += 1

q = int(input())
for i in range(q):
    s, t = map(int, input().split())
    if group[s] == group[t]:
        print("yes")
    else:
        print("no")

Python: # -*- coding: utf-8 -*-
from collections import deque

N, M = tuple(map(int, input().split()))
adj = [[] for n in range(N)]

for _ in range(M):
    inp = tuple(map(int, input().split()))
    adj[inp[0]].append(inp[1])
    adj[inp[1]].append(inp[0])

unsearched = set(range(N))
colors = {n:-1 for n in range(N)}
color = -1
while len(unsearched):
    color += 1
    start = min(unsearched)
    unsearched.remove(start)
    searched = set([start])
    
    que = deque([start])
    while len(que):
        q = que.pop()
        next_ = [i for i in adj[q] if  not (i in searched)]
        searched.update(next_)
        unsearched = unsearched.difference(searched)
        que.extendleft(next_)
    for n in searched:
        colors[n] = color
    
Q = int(input())

for i in range(Q):
    question = tuple(map(int, input().split()))
    if colors[question[0]] == colors[question[1]]:
        print("yes")        
    else:
        print("no")

Python: n, m = map(int, input().split())
relations = [[] for _ in range(n)]

for i in range(m):
    s, t = map(int, input().split())
    if s > t:
        s, t = t, s
    relations[s] += [t]
friend_id = [None] * n
for s, t in enumerate(relations):
    if t:
        queue = [s]
        while len(queue):
            k = queue.pop()
            friend_id[k] = s
            queue += relations[k]
            relations[k] = []

q = int(input())
for i in range(q):
    s, t = map(int, input().split())
    print('yes' if friend_id[s] and friend_id[s] == friend_id[t] else'no')

Python: from collections import deque
n,m = map(int,input().split())
G = [[] for _ in range(n)]
for i in range(m):
    s,t = map(int,input().split())
    s -= 1
    t -= 1
    G[s].append(t)
    G[t].append(s)

uni = [-1]*n
stk = deque()
def dfs(u,c):
    stk.append(u)
    while stk:
        u = stk.pop()
        uni[u] = c
        for v in G[u]:
            if uni[v] != -1: continue
            stk.append(v)

c = 0
for i in range(n):
    if uni[i] == -1:
        dfs(i,c)
        c += 1

q = int(input())
ans = ["no"]*q
for i in range(q):
    s,t = map(int,input().split())
    s -= 1
    t -= 1
    if uni[s] == uni[t]: ans[i] = "yes"

print("\n".join(ans))

Python: #coding:utf-8
#16D8101012J Ito Jun dj Python3

class UnionFind:
    def __init__(self,n):
        self.parent=[i for i in range(n+1)]
        self.rank=[0]*(n+1)
    def find(self,x):
        if self.parent[x] == x: # if x is x`s root
            return x
        else:
            self.parent[x] = self.find(self.parent[x])
            return self.parent[x]
    def is_same_tree(self,x,y):
        return self.find(x) == self.find(y) 
    def union(self,x,y):
        x=self.find(x)
        y=self.find(y)
        if self.rank[x] < self.rank[y]:
            self.parent[x] = y
        else:
            self.parent[y] = x
        if self.rank[x] == self.rank[y]:
            self.rank[x] += 1
        
def main():
    n=list(map(int,input().split()))
    union=UnionFind(n[0])
    friends=[]
    question=[]
    for i in range(n[1]):
        a=tuple(map(int,input().split()))
        friends.append(a)
    for i in friends:
        union.union(i[0],i[1])
    m=int(input())
    for i in range(m):
        b=tuple(map(int,input().split()))
        question.append(b)
    for i in question:
        if union.find(i[0]) == union.find(i[1]):
            print("yes")
        else:
            print("no")
if __name__ == "__main__":
    main()

Python: # -*- coding: utf-8 -*-
from collections import deque
import sys
sys.setrecursionlimit(100000)


if __name__ == '__main__':

    n, m = [int(s) for s in input().split(" ")]
    M = [set() for j in range(n)]
    for _ in range(m):
        u, v = [int(s) for s in input().split(" ")]
        M[u].add(v)
        M[v].add(u)
        
    color = [0] * n
    def dfs(u, c):  # depth-first search
        color[u] = c
        for v in M[u]:
            if color[v] == 0:
                dfs(v, c)
    
    c = 1
    for u in range(n):
        if color[u] == 0:
            dfs(u, c)
            c += 1
    
    l = int(input())
    for _ in range(l):
        p, q = [int(s) for s in input().split(" ")]
        if color[p] == color[q]:
            print("yes")
        else:
            print("no")