Go: package main

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

const (
	MAX = 100000
	NIL = -1
)

var (
	n     int
	G     [MAX][]int
	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)
			}
		}
	}
}

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() {
	var s, t, m, q int
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	scanner.Scan()
	n, _ = strconv.Atoi(scanner.Text())
	scanner.Scan()
	m, _ = strconv.Atoi(scanner.Text())
	for i := 0; i < m; i++ {
		scanner.Scan()
		s, _ = strconv.Atoi(scanner.Text())
		scanner.Scan()
		t, _ = strconv.Atoi(scanner.Text())
		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()
	scanner.Scan()
	q, _ = strconv.Atoi(scanner.Text())
	for i := 0; i < q; i++ {
		scanner.Scan()
		s, _ = strconv.Atoi(scanner.Text())
		scanner.Scan()
		t, _ = strconv.Atoi(scanner.Text())
		if color[s] == color[t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

Python: from enum import Enum
import sys
import math

BIG_NUM = 2000000000
MOD = 1000000007
EPS = 0.000000001


V,E = map(int,input().split())

boss = [i for i in range(V)]
height = [0 for i in range(V)]

def get_boss(index):
    if index == boss[index]:
        return index
    else:
        boss[index] = get_boss(boss[index])
        return boss[index]


def is_same_group(a,b):
    return get_boss(a) == get_boss(b)

def unite(x,y):
    boss_x = get_boss(x)
    boss_y = get_boss(y)

    if boss_x == boss_y:
        return

    if height[x] > height[y]:

        boss[boss_y] = boss_x

    elif height[x] < height[y]:

        boss[boss_x] = boss_y

    else:
        boss[boss_y] = boss_x
        height[x] += 1


for loop in range(E):
    A,B = map(int,input().split())
    unite(A,B)

num_query = int(input())

for loop in range(num_query):
    A,B = map(int,input().split())
    if is_same_group(A,B) == True:
        print("yes")
    else:
        print("no")

Python: #!/usr/bin/env python3

import array
import collections


UNDEF = -1


def compute_connected_components(max_v, adj_list):
    group = array.array("l", (UNDEF for _ in range(max_v)))
    g_idx = 0
    for u in range(max_v):
        if group[u] == UNDEF:
            group[u] = g_idx
            q = collections.deque()
            q.append(u)
            while q:
                v = q.popleft()
                for w in adj_list[v]:
                    if group[w] == UNDEF:
                        group[w] = g_idx
                        q.append(w)
            else:
                g_idx += 1
    return group


def main():
    n, m = map(int, input().split())
    adj_list = [set() for _ in range(n)]
    for _ in range(m):
        s, t = map(int, input().split())
        adj_list[s].add(t)
        adj_list[t].add(s)
    group = compute_connected_components(n, adj_list)
    q = int(input())
    for _ in range(q):
        s, t = map(int, input().split())
        print("yes" if group[s] == group[t] else "no")


if __name__ == '__main__':
    main()

Python: # -*- coding: utf-8 -*-


class LinkedList:
    def __init__(self, n):
        self.n = n
        self.ll = [[] for _ in range(self.n)]

    def link(self, u, v, direction=False):
        self.ll[u].append(v)
        if not direction:
            self.ll[v].append(u)

    def dfs(self):
        self.cc = [None] * self.n

        color = 1
        for u in range(self.n):
            if not self.cc[u]:
                self.dfs_visit(u, color)
                color += 1

    def dfs_visit(self, u, color):
        self.cc[u] = color
        for v in self.ll[u]:
            if not self.cc[v]:
                self.dfs_visit(v, color)

    def check(self, u, v):
        if self.cc[u] == self.cc[v]:
            print('yes')
        else:
            print('no')


if __name__ == '__main__':
    n, m = map(int, input().split())
    ll = LinkedList(n)

    for _ in range(m):
        u, v = map(int, input().split())
        ll.link(u, v)
    ll.dfs()

    q = int(input())
    for _ in range(q):
        u, v = map(int, input().split())
        ll.check(u, v)

Python: import sys

def Grouping(F):
    n = len(F)
    G = [None for i in range(n)]
    for u in range(n):
        if G[u] is None:
            G[u] = u
            S = [u]
            while(len(S) > 0):
                u1 = S.pop()
                for u2 in F[u1]:
                    if G[u2] is None:
                        G[u2] = u
                        S.append(u2)
    return G

def main():
    istr = sys.stdin.read()
    ilist = istr.splitlines()
    unum, fnum = list(map(int,ilist[0].split()))

    F = [[]  for i in range(unum)]
    fnum += 1
    for n in range(1, fnum):
        uid, fid = map(int,ilist[n].split())
        F[uid].append(fid)
        F[fid].append(uid)
    
    G = Grouping(F)

    qnum = int(ilist[fnum])
    fnum += 1
    for q in range(fnum, (fnum + qnum)):
        id1, id2 = map(int,ilist[q].split())
        if G[id1] == G[id2]:
            print("yes")
        else:
            print("no")

if __name__ == '__main__':
    main()

Python: def MAIN():
    n, m = map(int, input().split())
    li = [i for i in range(n)]
    def f(a):
        if li[a] == a:
            return a
        b = f(li[a])
        li[a] = b
        return b
    def solve(a, b):
        if f(a) == f(b):
            return "yes"
        return "no"
    for _ in range(m):
        x, y = map(int, input().split())
        if li[x] > li[y]:
            li[x] = li[y]
        else:
            li[y] = li[x]
    for _ in range(int(input())):
        x, y = map(int, input().split())
        print(solve(x, y))
MAIN()

Python: def dfs(r, c):
    global color, G
    S = [r]
    color[r] = c
    while (0 < len(S)):
        u = S.pop()
        for u in G[u]:
            v = color[u]
            if (v == None):
                color[u] = c
                S.append(u)
 
def assignColor():
    global color, G, 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 = [None 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 = [False 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: 
def BFS(s = 0, group_num = 0):
    Q.pop(0)
    color[s] = 2
    for j in range(len(A[s])):
        if color[A[s][j]] == 0:
            Q.append(A[s][j])
            color[A[s][j]] = 1
            affil[A[s][j]] = group_num
    if len(Q) != 0:
        BFS(Q[0], group_num)

entry = map(int, raw_input().split())
n = entry[0]
m = entry[1]

A = range(n)
for i in A:
    A[i] = list()
for i in range(m):
    entry = map(int, raw_input().split())
    s = entry[0]
    t = entry[1]
    A[s].append(t)
    A[t].append(s)

color = [0] * n
affil = [0] * n
group_num = -1
for i in range(n):
    if color[i] == 0:
        Q = [i]
        group_num = group_num + 1
        affil[i] = group_num
        BFS(i, group_num)

q = int(raw_input())
for i in range(q):
    entry = map(int, raw_input().split())
    if affil[entry[0]] == affil[entry[1]]:
        print("yes")
    else:
        print("no")