Go: package main

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

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	nNodes := scanInt(sc)
	nConns := scanInt(sc)

	graph := make([][]int, nNodes)
	for i := 0; i < nConns; i++ {
		a, b := scanInt(sc), scanInt(sc)
		graph[a] = append(graph[a], b)
		graph[b] = append(graph[b], a)
	}

	groups := make([]int, nNodes)

	var setGroups func(int, int)
	setGroups = func(u int, groupId int) {
		if groups[u] > 0 {
			return
		}
		groups[u] = groupId

		for _, v := range graph[u] {
			setGroups(v, groupId)
		}
	}
	for i := 0; i < nNodes; i++ {
		setGroups(i, i+1)
	}

	nQuestions := scanInt(sc)

	w := bufio.NewWriter(os.Stdout)
	var ans string
	for i := 0; i < nQuestions; i++ {
		a, b := scanInt(sc), scanInt(sc)
		if groups[a] == groups[b] {
			ans = "yes"
		} else {
			ans = "no"
		}
		fmt.Fprintln(w, ans)
	}
	w.Flush()
}

func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

Python: def bfs(s, t):
  q = [s]
  visited = []
  while len(q) > 0:
    v = q.pop(0)
    if v == t: return True
    if v not in visited and len(G[v]) > 0:
      q.extend(sorted(G[v]))
      visited.append(v)
  return False

u, n = map(int, input().split())
G = [[] for _ in range(u)]
for _ in range(n):
  a, b = map(int, input().split())
  if b not in G[a]: G[a].append(b)
  if a not in G[b]: G[b].append(a)

q = int(input())
for _ in range(q):
  s, t = map(int, input().split())
  if bfs(s, t):
    print("yes")
  else:
    print("no")

Python: # coding: UTF-8
from collections import deque
n,m = map(int,input().split())
link = [[] for _ in range(n)]
part = [-1 for _ in range(n)]
for _ in range(m):
  u,v = map(int,input().split())
  link[u].append(v)
  link[v].append(u)

searched = set()
queue = deque()
pindex = 0
for u in range(n):
  if u not in searched:
    queue.append(u)
    pindex += 1
    searched.add(u)
    while queue:
      v = queue.popleft()
      part[v] = pindex
      for w in link[v]:
        if w not in searched:
          part[w] = pindex
          queue.append(w)
          searched.add(w)

q = int(input())
answers = []
for _ in range(q):
  s,t = map(int,input().split())
  if part[s] == part[t]:
    answers.append("Yes")
  else:
    answers.append("No")

for answer in answers:
  print(answer)

Python: n, m = map(int, input().split())
a = [[False]*n for i in range(n)]
rootList = [-1] * n

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

Python: from collections import deque


def dfs(G, C, id, color):
    S = deque()
    S.append(id)
    C[id] = color

    while S:
        u = S.pop()
        #S = S[:-1]  # pop
        for i in range(len(G[u])):
            v = G[u][i]
            if C[v] == -1:
                C[v] = color
                S.append(v)


if __name__ == '__main__':
    # ??????????????\???
    num_of_users, num_of_links = [int(x) for x in input().split(' ')]
    links = []
    for _ in range(num_of_links):
        links.append(list(map(int, input().split(' '))))
    num_of_queries = int(input())
    queries = []
    for _ in range(num_of_queries):
        queries.append(list(map(int, input().split(' '))))

    # ???????????????
    G = [[] for _ in range(100000)]
    C = [-1] * 100000
    for f, t in links:
        G[f].append(t)
        G[t].append(f)

    color = 1
    for id in range(num_of_users):
        if C[id] == -1:
            dfs(G, C, id, color)
        color += 1

    # ???????????????
    for x, y in queries:
        if C[x] == C[y]:
            print('yes')
        else:
            print('no')

Python: n = list(map(int,input().split()))
cn = [i for i in range(n[0])]
cnt = [[0]]*n[0]
for i in range(1,n[0]):
    cnt[i] = [i]
x = [1]*n[0]

for i in range(n[1]):
    a = list(map(int,input().split()))
    if cn[a[0]] != cn[a[1]]:
        if x[a[0]] > x[a[1]]: 
            tmp = cn[a[1]]
            tmp2 = cn[a[0]]
        else: 
            tmp = cn[a[0]]
            tmp2 = cn[a[1]]
        for j in cnt[tmp]:
            cn[j] = cn[tmp2]
        x[tmp2] += len(cnt[tmp])
        cnt[tmp2].extend(cnt[tmp])
        cnt[tmp] = [-1]

q = int(input())
for i in range(q):
    a = list(map(int,input().split()))
    if cn[a[0]] == cn[a[1]]: print("yes")
    else: print("no")

Python: n, m = map(int, input().split())
*p, = range(n)
def root(s):
    if s == p[s]:
        return p[s]
    p[s] = s = root(p[s])
    return s
def unite(a, b):
    aa = root(a);bb = root(b)
    if aa < bb:
        p[bb] = aa
    else:
        p[aa] = bb
        
for i in range(m):
    s, t = map(int, input().split())
    unite(s, t)
N = int(input())
*_, = map(root, range(n))

ans = []
for i in range(N):
    s, t = map(int, input().split())
    ans.append('yes' if p[s] == p[t] else 'no')
print('\n'.join(ans))

Python: # -*- coding: utf_8 -*-

level = False
def debug(v):
    if level:
        print(v)

NOT_FOUND = 0
ENQUEUED = 1
FOUND = 2

def bfs(graph, start, target):
    debug(graph)
    if start == target:
        return True
    
    queue = []
    status = [NOT_FOUND] * len(graph)
    queue.append(start)

    while len(queue) != 0:
        debug("----------------------------")
        node = queue.pop(0)
        status[node] = FOUND
        edges = graph[node]
        debug(queue)
        debug(status)
        debug(edges)
        for e in edges:
            if e == target:
                return True
            if status[e] == NOT_FOUND:
                status[e] = ENQUEUED
                queue.append(e)

    return False

if __name__ == "__main__":
    n, m = [int(x) for x in input().split()]

    g = [[] for i in range(n)]
    for i in range(m):
        u, e = [int(x) for x in input().split()]
        g[u].append(e)
        g[e].append(u)

    n = int(input())
    for i in range(n):
        s, d = [int(x) for x in input().split()]
        if bfs(g, s, d):
            print("yes")
        else:
            print("no")

Python: def dfs(G, s):
    # ????????????
    S = [s]
    # ?¨??????????????????????
    C = set([s])
    while len(S) > 0:
        v = S.pop()
        for w in G[v]:
            if w not in C:
                S.append(w)
                C |= set([w])
    return C


if __name__ == '__main__':
    n, m = map(int, input().split())
    G = {key: [] for key in range(n)}
    for i in range(m):
        s, t = map(int, input().split())
        G[s].append(t)
        G[t].append(s)

    q = int(input())
    for _ in range(q):
        s, t = map(int, input().split())
        if t in dfs(G, s):
            print('yes')
        else:
            print('no')

Python: n, m = map(int, input().split())

adj = [[] for i in range(n)]

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

isVisited = [False] * n

CC = [None] * n


def dfs(u, group):
    isVisited[u] = True
    CC[u] = group
    for v in adj[u]:
        if not isVisited[v]:
            dfs(v, group)

def makeCC(group):
    for i in range(n):
        if not isVisited[i]:
            dfs(i, group)
            group += 1

def isConnected(v1, v2):
    if CC[v1] == CC[v2]:
        print('yes')
    else:
        print('no')


makeCC(0)


q = int(input())

for i in range(q):
    s, t = map(int, input().split())
    isConnected(s, t)