Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	n, err := strconv.Atoi(nextString())
	if err != nil {
		fmt.Printf("strconv.Atoi failed: %v\n", err)
	}
	return n
}

func newGraph(nNodes int) *Graph {
	g := Graph{}
	g.nodes = make([]*GraphNode, nNodes)
	for iNode := 0; iNode < len(g.nodes); iNode++ {
		g.nodes[iNode] = &GraphNode{}
		g.nodes[iNode].key = GraphNodeKey(iNode)
	}
	return &g
}

var infty = 1000000000

type GraphNodeKey int

// GraphNode is a node for undirected graph
type GraphNode struct {
	key       GraphNodeKey
	adjacents []*GraphNode
	visited   bool
	d, f      int
	parent    *GraphNode
	cc        int
}

func (g *Graph) setAdjacent(l, r GraphNodeKey) {
	g.nodes[l].adjacents = append(g.nodes[l].adjacents, g.nodes[r])
}

// Graph is a undirected graph
type Graph struct {
	nodes []*GraphNode
}

func (g *Graph) initialize() {
	for iNode := 0; iNode < len(g.nodes); iNode++ {
		g.nodes[iNode].visited = false
		g.nodes[iNode].d = infty
		g.nodes[iNode].f = infty
		g.nodes[iNode].parent = nil
		g.nodes[iNode].cc = -1 // 22.3-12
	}
}

type QueueEntry struct {
	node *GraphNode
	next *QueueEntry
}

type Queue struct {
	head, tail *QueueEntry
}

func (q *Queue) enqueue(node *GraphNode) {
	entry := QueueEntry{}
	entry.node = node

	if q.tail == nil {
		q.head = &entry
		q.tail = &entry
		return
	}

	q.tail.next = &entry
	q.tail = q.tail.next
}

func (q *Queue) dequeue() *QueueEntry {
	if q.head == nil {
		return nil
	}
	poped := q.head
	q.head = q.head.next
	if q.head == nil {
		q.tail = nil
	}
	return poped
}

func (q *Queue) isEmpty() bool {
	return q.head == nil
}

var time = 0

func fillDistancesByDepthFirstSearch(g *Graph) {
	g.initialize()
	time = 0
	cc := 0

	for _, u := range g.nodes {
		if !u.visited {
			dfsVisit(g, u, cc)
			cc++
		}
	}
}

func dfsVisit(g *Graph, u *GraphNode, cc int) {
	time++
	u.d = time
	u.cc = cc

	u.visited = true
	for _, v := range u.adjacents {
		if !v.visited {
			v.parent = u
			dfsVisit(g, v, cc)
		}
	}
	time++
	u.f = time
}

func main() {
	scanner.Split(bufio.ScanWords)

	nUsers := nextInt()
	nEdges := nextInt()
	graph := newGraph(nUsers)
	for iEdge := 0; iEdge < nEdges; iEdge++ {
		l := GraphNodeKey(nextInt())
		r := GraphNodeKey(nextInt())
		graph.setAdjacent(l, r)
		graph.setAdjacent(r, l)
	}

	fillDistancesByDepthFirstSearch(graph)

	nQueries := nextInt()
	for iQuery := 0; iQuery < nQueries; iQuery++ {
		l := GraphNodeKey(nextInt())
		r := GraphNodeKey(nextInt())

		// fmt.Println(graph.nodes[l].d, graph.nodes[r].d, graph.nodes[r].f, graph.nodes[l].f)
		if graph.nodes[l].cc == graph.nodes[r].cc {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

Python: v, e = map(int, input().split())   #ユーザ数、関係性の数
edge = [[] for _ in range(v)]      #お隣さんリスト


#連結成分作成部分のコード（各頂点を一度ずつ訪問して隣接リスト内の辺を訪問）
for _ in range(e):                 #関係性の数だけ
  s, t = map(int, input().split()) #始点と終点を入れる
  edge[s].append(t)                #sのお隣さんリストにtを
  edge[t].append(s)                #tのお隣さんリストにsを

group = [-1]*v                     #グループというリストを作る（こいつの値であとで友達か照合）
cnt = 0                            #グループ番号


#隣接リストに入っている同じエッジをスタックに入れてグループ化する
for i in range(v):
  if group[i] == -1:
    group[i] = cnt                 #カウントの値を入れる
    stack = [i]                    #エッジ番号を入れる
    while stack:
      v = stack.pop()              #エッジを代入　ー①
      for c in edge[v]:            #①のエッジのお隣さんリストを辿っていく
        if group[c] == -1:         #お隣さんのグループが初期化状態なら
          group[c] = cnt          #グループリストにカウントを入れる
          stack.append(c)          #スタックにお隣さんを入れる
    cnt += 1                       #お隣さんの訪問が終わったらグループ番号を変える

#クエリのコード
for _ in range(int(input())):
  s, t = map(int, input().split())
  print('yes' if group[s] == group[t] else 'no')

Python: 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 = {}
c = 0
for i in range(n):
    if not i in group:
        que = [i]
        group[i] = c
        while len(que) > 0:
            u = que[0]
            for j in G[u]:
                if not j in group:
                    group[j] = que.append(j)
            del que[0]
        c += 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: import sys
input = sys.stdin.readline

from collections import deque, defaultdict
from copy import deepcopy

MAX = 100000
NIL = -1

#グラフGはdictで管理する
G = defaultdict(lambda:deque())
color = [NIL]*MAX

#頂点r,探索ごとに異なる数cによって深さ優先探索をする関数
#つながっている部分は全て色が同じになる
def dfs(r, c):
    S = deque()
    S.append(r) 
    color[r] = c
    while S: #Sが存在する間以下の処理を実行
        u = S.popleft()
        for v in G[u]:#Gのvalueはqueueとなっている
            if color[v] == NIL:#色がない場合のみ以下の操作を行う
                color[v] = c
                S.append(v) #深さを深くして次の頂点を探す準備をする

def make_color():
    id = 1
    for u in range(n):
        if color[u] == NIL:
            dfs(u, id) #色を塗る
            id += 1 #色を変える
        
    
    
n, m = map(int, input().split())

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

make_color()

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

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")