Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	m := getNextInt(scanner)
	nodes := make([]Node, n)

	for i := 0; i < n; i++ {
		nodes[i].list = make([]int, 0)
	}

	for i := 0; i < m; i++ {
		s := getNextInt(scanner)
		t := getNextInt(scanner)
		nodes[s].list = append(nodes[s].list, t)
		nodes[t].list = append(nodes[t].list, s)
	}

	c := 1
	for i := 0; i < n; i++ {
		if nodes[i].c == 0 {
			traverse(nodes, i, c)
			c++
		}
	}

	q := getNextInt(scanner)

	for i := 0; i < q; i++ {
		s := getNextInt(scanner)
		t := getNextInt(scanner)
		if nodes[s].c == nodes[t].c {
			fmt.Fprintln(writer, "yes")
			continue
		}
		fmt.Fprintln(writer, "no")
	}

	writer.Flush()
}

// Node ...
type Node struct {
	list []int
	c    int
}

func traverse(nodes []Node, r, c int) {
	nodes[r].c = c
	for _, i := range nodes[r].list {
		if nodes[i].c != 0 {
			continue
		}
		traverse(nodes, i, c)
	}
}

Python: from collections import deque

n, m = map(int, input().split())
g = [set() for _ in range(n)]

while m:
    s, t = map(int, input().split())
    g[s].add(t)
    g[t].add(s)
    m -= 1


def find(s, t):
    global g
    queue = deque()
    queue.append((0, s))
    queue.append((1, t))
    visited = ([0] * n, [0] * n)
    visited[0][s] = 1
    visited[1][t] = 1

    def remember(visited, new):
        for i, v in enumerate(visited):
            if v:
                g[new].add(i)
                g[i].add(new)
        visited[new] = 1

    while queue:
        st, i = queue.popleft()
        for f in g[i]:
            if visited[not st][f]:
                return True
            if not visited[st][f]:
                remember(visited[st], f)
                queue.append((st, f))
    return False


q = int(input())
while q:
    s, t = map(int, input().split())
    print('yes' if find(s, t) else 'no')
    q -= 1

Python: n, m = map(int, input().split())
rootList = [-1 for i in range(n)]
 
def getRoot(x):
    if rootList[x] < 0:
        rootList[x] = x
        return x
    return getRoot(rootList[x])
 
 
def setSameRoot(x, y):
    x = getRoot(x)
    y = getRoot(y)
    if x != y:
        rootList[x], rootList[y] = min(x, y), min(x, y)
 
for i in range(m):
    s, t = map(int, input().split())
    setSameRoot(s, t)
q = int(input())
for i in range(q):
    s, t = map(int, input().split())
    print("yes" if getRoot(s) == getRoot(t) != -1 else "no")

Python: class UnionFind:
    def __init__(self,n):
        self.n = n
        self.p = [i for i in range(n)]
        self.rank = [0]*n

    def same(self,x,y):
        return self.root(x)==self.root(y)

    def root(self,x):
        if x!=self.p[x]:self.p[x] = self.root(self.p[x])
        return self.p[x]

    def unite(self,x,y):
        x = self.root(x)
        y = self.root(y)
        if self.rank[y]<self.rank[x]:
            self.p[y] = x
        else:
            self.p[x] = y
            if self.rank[y]==self.rank[x]:
                self.rank[y]+=1

def main():
    n,m = map(int,input().split())
    UF = UnionFind(n)
    for _ in range(m):
        a,b = map(int,input().split())
        UF.unite(a,b)
    q = int(input())
    for _ in range(q):
        a,b = map(int,input().split())
        if UF.same(a,b):print ('yes')
        else           :print ('no')


if __name__ == '__main__':
    main()

Python: from collections import deque


user_num,rer_num=map(int,input().split())
graph=[[] for loop in range(user_num)]

for loop in range(rer_num):
    user1,user2=map(int,input().split())
    graph[user1].append(user2)
    graph[user2].append(user1)

#group[user1]はuser1が属するグループ.同じグループに属するuser同士は互いに到達可能
group=[-1]*user_num

que=deque([])
que.append(0)
tmp_group=0
for user in range(user_num):
    if(group[user]==-1):
        que.append(user)
        group[user]=tmp_group
        while(1):
            user1=que.popleft()
            for user2 in graph[user1]:
                if(group[user2]==-1):
                    que.append(user2)
                    group[user2]=tmp_group
            if(len(que)==0):
                tmp_group+=1
                break

for loop in range(int(input())):
    user1,user2=map(int,input().split())
    if(group[user1]==group[user2]):
        print("yes")
    else:
        print("no")

Python: from collections import defaultdict
user_num, conn_num = (int(n) for n in input().split(" "))
conn = defaultdict(list)
for _ in range(conn_num):
    i, j = (int(n) for n in input().split(" "))
    conn[i].append(j)
    conn[j].append(i)
find = [-1 * n - 1 for n in range(user_num)]
query = int(input())
for q_num in range(query):
    one, theother = (int(n) for n in input().split(" "))
    if find[one] != find[theother] and find[one] < 0:
        queue = [one]
        find[one] = q_num
        while queue:
            new_queue = []
            for q in queue:
                for c in conn[q]:
                    if find[c] < 0:
                        new_queue.append(c)
                        find[c] = q_num
            queue = new_queue
    if find[one] == find[theother]:
        print("yes")
    else:
        print("no")

Python: from collections import deque


def CC():
    id=0
    color=["white" for i in range(n)]
    for j in range(n):
        if color[j]=="white":
            color[j]="gray"
            queue=deque([j])

            while len(queue)!=0:
                u=queue.popleft()
                for i in M[u]:
                    if color[i]=="white":
                        color[i]="gray"
                        queue.append(i)
                color[u]=str(id)
            id +=1

    return color


n,m=map(int,input().split())
M=[[] for i in range(n)]
for i in range(m):
    p,q=map(int,input().split())
    M[p].append(q)
    M[q].append(p)

color=CC()

for i in range(int(input())):
    a,b=map(int,input().split())
    print("yes" if color[a]==color[b] else "no")

Python: # Connected Components
from collections import defaultdict
import sys
sys.setrecursionlimit(1 << 25)  # 再起上限引き上げ

G = defaultdict(lambda: [])

# load data
N, M = list(map(int, input().split()))
color = {key: None for key in range(N)}  # 色というかグループ #intで表す #Noneは未訪問を示す
# graphをdefault dictで保持することにする。
for _ in range(M):
    s, t = list(map(int, input().split()))
    G[s].append(t)
    G[t].append(s)

def dfs(node: int, co: int):
    if color[node] is not None:
        return
    color[node] = co
    for n in G[node]:
        dfs(n, co)
    return

# すべてのnodeを開始点としてdfsで領域わけしてみる
c = 1
for node in G.keys():
    dfs(node, c)  # 訪問済みだったら色を塗り替えないというないようはdfs関数内の処理で吸収できる
    c += 1

# 問題に回答していく
Q = int(input())
for _ in range(Q):
    s, t = list(map(int, input().split()))
    if ((color[s] is not None) and (color[t] is not None)) and (color[s] == color[t]):
        # s,tも友達がいて、かつ同じグループだったら
        print('yes')
    else:
        print('no')