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: import sys
sys.setrecursionlimit(200000)

def dfs(v):
    global node_chk
    global edge_chk
    global B
    global connect
    global value

    node_chk[v] = 1
    connect[v] = value
    for x in B[v]:
        if(node_chk[x] == 0):
                dfs(x)



n,m = map(int,input().split())
B = [[]for i in range(n)] # 隣接リスト
edge_chk = [[]for i in range(n)]
node_chk = [0 for i in range(n)]
connect = [0 for i in range(n)]
value = 0

for i in range(m):
    A = list(map(int,input().split()))
    B[A[0]].append(A[1])
    B[A[1]].append(A[0])
    edge_chk[A[0]].append(0)
    edge_chk[A[1]].append(0)

for i in range(n):
    if(node_chk[i] == 1):
        continue
    dfs(i)
    value += 1


q = int(input())
for i in range(q):
    start,target = map(int,input().split())
    if(connect[start] == connect[target]):
        print("yes")
    else:
        print("no")

Python: from queue import deque

n, m = map(int, input().split())
G = deque([[] for i in range(n)]) #??°??????
for i in range(m):
    s, t = map(int, input().split())
    # ???????????£?????????????????????1????????\??????0
    G[s].append(t)
    G[t].append(s)


def dfs(r, c):
    S = deque()
    S.append(r)
    color[r] = c
    while (len(S) > 0):
        u = S.popleft()
        for j in G[u]:
            if color[j] == -1:
                # ???????????£???????????????????????¢?´¢????????????(???????????¢?´¢?????????????????????)
                color[j] = c
                S.append(j) # ?????????????????????????????¢???

def assginColor():
    i_d = 1
    for u in range(n):
        if color[u] == -1: #?????¢?´¢
            dfs(u, i_d)
            i_d += 1

color = [-1] * n
assginColor()
q = int(input())
s_t = [list(map(int, input().split())) for i in range(q)]
for s, t in s_t:
    if color[s] == color[t]:
        print("yes")
    else:
        print("no")

Python: #!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys


def assign_color():
    _id = 1
    for m in range(vertices_num):
        if vertices_status_list[m] == -1:
            graph_dfs(m, _id)
            _id += 1
    return None


def graph_dfs(vertex, color):
    vertices_stack = list()
    vertices_stack.append(vertex)
    vertices_status_list[vertex] = color
    while vertices_stack:
        current_vertex = vertices_stack[-1]
        vertices_stack.pop()
        for v in adj_list[current_vertex]:
            if vertices_status_list[v] == -1:
                vertices_status_list[v] = color
                vertices_stack.append(v)
    return None


if __name__ == '__main__':
    _input = sys.stdin.readlines()
    vertices_num, relation_num = map(int, _input[0].split())

    relation_info = _input[1:relation_num + 1]

    question_num = int(_input[relation_num + 1])
    question_list = _input[relation_num + 2:]

    adj_list = [[] for _ in range(vertices_num)]
    vertices_status_list = [-1] * vertices_num

    for relation in relation_info:
        key, value = int(relation[0]), int(relation[2])
        adj_list[key].append(value)
        adj_list[value].append(key)

    assign_color()

    # print(adj_list)
    for question in question_list:
        start, target = int(question[0]), int(question[2])
        if vertices_status_list[start] == vertices_status_list[target]:
            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

import sys
sys.setrecursionlimit(10000)

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)

Python: def tan(G,st,fi):
    global flag
    for i in range(len(G)):
        if G[st][i] == 1:
            if i == fi:
                flag = 1
            tan(G,i,fi)
    
n,m = list(map(int, input().split()))
G = [[0 for i in range(n)] for j in range(n)]

for i in range(m):
    S = list(map(int, input().split()))
    if S[0]<S[1]:
        G[S[0]][S[1]] = 1
    else:
        G[S[1]][S[0]] = 1

q = int(input())
ans = []
for i in range(q):
    Q = list(map(int, input().split()))
    if Q[0]<Q[1]:
        st = Q[0]
        fi = Q[1]
    else:
        st = Q[1]
        fi = Q[0]

    flag = 0
    tan(G,st,fi)
    if flag==1:
        ans.append("yes")
    else:
        ans.append("no")
        
for i in range(q):
    print(ans[i])

Python: # ALDS1_11_D Connected Components
import sys
import queue


sys.setrecursionlimit(1000000)

def check(adj, foot_print):
    n = len(foot_print)
    que = queue.Queue()
    num = 0
    for i in range(n):
        if foot_print[i] == 0:
            num += 1
            que.put(i)
            foot_print[i] = num
            bfs(adj, que, foot_print, num)


def bfs(adj, que, foot_print, num):
    if not que.empty():
        now = que.get()
        for i in adj[now]:
            if foot_print[i] == 0:
                foot_print[i] = num
                que.put(i)
        bfs(adj, que, foot_print, num)
    else:
        return


def main():
    n, m = map(int, sys.stdin.readline().strip().split())
    adj_list = [[] for _ in range(n)]
    for i in range(m):
        s, t = map(int, sys.stdin.readline().strip().split())
        adj_list[s].append(t)
        adj_list[t].append(s)

    foot_print = [0] * n
    check(adj_list, foot_print)

    q = int(input())
    for i in range(q):
        s, t = map(int, sys.stdin.readline().strip().split())
        if foot_print[s] == foot_print[t]:
            print('yes')
        else:
            print('no')


if __name__ == '__main__':
    main()

Python: n, m = map(int, input().split())
rootList = [-1] * n

def getRoot(x):
    if rootList[x] < 0:
        return x
    return getRoot(rootList[x])


def setSameRoot(x, y):
    x = getRoot(x)
    y = getRoot(y)
    if x != y:
        G[x], G[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) else "no")