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: 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 = map(int,input().split())
color = {key: None for key in range(N)}
#graphをdefaultdictで保持することにする
for _ in range(M):
    s,t = map(int,input().split())
    G[s].append(t)
    G[t].append(s)

#隣接リストを基にたどり着ける友達をグループ化する。
def dfs(node:int, co:int):
    #終了条件、既に訪問済みなら訪問しない
    if color[node] is not None:
        return
    #処理
    color[node] = co
    for n in G[node]:
        dfs(n,co)

    return

#全てのnodeを開始点としてdfsで色分けしてみる
c = 1
for node in G.keys():
    dfs(node,c)
    c += 1

#問題への解答
Q = int(input())
for _ in range(Q):
    s,t = map(int,input().split())
    if (color[s] is not None) and (color[t] is not None) and (color[s] == color[t]):
        print('yes')
    else:
        print('no')

Python: #Union Find

#xの根を求める
def find(x):
    if par[x] < 0:
        return x
    else:
        par[x] = find(par[x])
        return par[x]
#xとyの属する集合の併合
def unite(x,y):
    x = find(x)
    y = find(y)
    
    if x == y:
        return False
    else:
        #sizeの大きいほうがx
        if par[x] > par[y]:
            x,y = y,x
        par[x] += par[y]
        par[y] = x
        return True

#xとyが同じ集合に属するかの判定
def same(x,y):
    return find(x) == find(y)

#xが属する集合の個数
def size(x):
    return -par[find(x)]

#初期化
#根なら-size,子なら親の頂点
n,m = map(int,input().split())
par = [-1]*n
for i in range(m):
  x,y = map(int,input().split())
  unite(x,y)

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

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

def are_connected(s, t):
    q = [s]
    checked = [False] * n
    checked[s] = True

    while q:
        user = q.pop(0)
        for f in friend[user]:
            if f == t:
                print(f, user)
                return True
            elif not checked[f]:
                q.append(f)
                checked[f] = True
    return False

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

Python: import sys
import os
import pprint

#fd = os.open('ALDS1_11_D-3.txt', os.O_RDONLY)
#os.dup2(fd, sys.stdin.fileno())

"""connected components"""

l = list(map(int, input().split()))
DEBUG = False

# node num
n = l[0]

# relation num
m = l[1]

# each node color
colors = [None] * n

rel_list = []
for _ in range(n):
    rel_list.append([])
# relation
for _ in range(m):
    l = list(map(int, input().split()))
    s = l[0]
    t = l[1]
    rel_list[s].append(t)
    rel_list[t].append(s)

if DEBUG:
    print(rel_list)

# coloring by DFS or BFS
for node_index in range(n):

    stack = []
    if colors[node_index] is None:
        stack.append(node_index)
        while stack:
            # process top of stack
            top = stack.pop()
            colors[top] = node_index

            relations = rel_list[top]
            for relation in relations:
                if colors[relation] is None:
                    stack.append(relation)

if DEBUG:
    print(colors)

# question num
q = int(input())

for _ in range(q):
    l = list(map(int, input().split()))
    s = l[0]
    t = l[1]
    if colors[s] == colors[t]:
        print('yes')
    else:
        print('no')

Python: def dfs(r, c):
    global color
    global g
    s = [r]
    color[r] = c
    while len(s) > 0:
        u = s.pop()
        for u in g[u]:
            v = color[u]
            if v is None:
                color[u] = c
                s.append(u)
                
def assigncolor():
    global g
    global color
    global n
    c = 1
    for i in range(n):
        if color[i] == None:
            dfs(i, c)
            c += 1
            
n, m = list(map(int, input().split()))

g = [[] for i in range(n)]
for i in range(m):
    s, t = list(map(int, input().split()))
    g[s].append(t)
    g[t].append(s)
    
color = [None for i in range(n)]

assigncolor()

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

Python: import sys
def s():
 e=sys.stdin.readline
 n,m=map(int,e().split())
 P=[[]for _ in[0]*n]
 C=[0]*n
 k=0
 for _ in[0]*m:
  s,t=map(int,e().split());P[s]+=[t];P[t]+=[s]
 for i in range(n):
  k+=1
  if C[i]<1:
   s=[i];C[i]=k
   while s:
    u=s.pop()
    for v in P[u]:
     if C[v]<1:C[v]=k;s+=[v]
 for _ in[0]*int(e()):
  a,b=map(int,e().split())
  print(['no','yes'][C[a]==C[b]])
if'__main__'==__name__:s()

Python: #coding: utf-8
n, m = map(int,input().split())
List = [[] for i in range(n)]
color = ["white" for i in range(n)]

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


def search(a,target):
    for member in List[a]:
        if member == target:
            print("yes")
            return True
        if color[member] == "white":
            color[member] = "black"
            return search(member, target)

p = int(input())
for i in range(p):
    a, target = map(int,input().split())
    b = search(a, target)
    if b != True:
        print("no")