Go: package main

import (
	"bufio"
	"container/list"
	"fmt"
	"os"
	"strconv"
)

//util
var sc = bufio.NewScanner(os.Stdin)

func nextStr() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func printList(list []int) {
	n := len(list)
	buf := bufio.NewWriter(os.Stdout)
	for _, v := range list[0 : n-1] {
		buf.Write([]byte(fmt.Sprintf("%d ", v)))
	}
	buf.Write([]byte(fmt.Sprintf("%d\n", list[n-1])))
	buf.Flush()
}

func max(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}

func min(a, b int) int {
	if a > b {
		return b
	} else {
		return a
	}
}

//solve
const (
	MAX = 100000
	NIL = -1
)

var (
	n, m, q, s, t int
	G             [MAX][]int //連結リスト
	color         [MAX]int
)

func dfs(r int, c int) {
	S := list.New()
	S.PushFront(r)
	color[r] = c
	for S.Len() != 0 {
		u := S.Remove(S.Front()).(int)
		for i := 0; i < len(G[u]); i++ {
			v := G[u][i]
			if color[v] == NIL {
				color[v] = c
				S.PushFront(v)
			}
		}
	}
}

//幅優先探索で、頂点を色付け
func assignColor() {
	id := 1
	for i := 0; i < n; i++ {
		color[i] = NIL
	}
	for i := 0; i < n; i++ {
		if color[i] == NIL {
			id++
			dfs(i, id)
		}
	}
}

func main() {
	sc.Split(bufio.ScanWords)
	n, m = nextInt(), nextInt()
	for i := 0; i < m; i++ {
		s, t = nextInt(), nextInt()
		if i == 0 {
			G[s] = make([]int, 0)
			G[t] = make([]int, 0)
		}
		G[s] = append(G[s], t)
		G[t] = append(G[t], s)

	}
	assignColor()
	q = nextInt()
	for i := 0; i < q; i++ {
		s, t = nextInt(), nextInt()
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}

}

Python: from collections import deque

def bfs(graph, start, goal, connection):
    visited = {start: None}
    unvisited = deque()
    unvisited.append(start)
    while unvisited:
        now = unvisited.popleft()
        if now == goal or goal in c[now]:
            c[start].add(goal)
            c[goal].add(start)
            return "yes"
        for next in graph[now]:
            if not (next in visited):
                unvisited.append(next)
                visited[next] = now
    return "no"

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

for i in range(m):
    inp = list(map(int, input().split()))
    g[inp[0]].append(inp[1])
    g[inp[1]].append(inp[0])
    c[inp[0]].add(inp[1])
    c[inp[1]].add(inp[0])

q = int(input())

for i in range(q):
    s, t = map(int, input().split())
    print(bfs(g, s, t, 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])