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: 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()