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 collections import deque

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

while m:
    s, t = map(int, input().split())
    g[s].add(t)
    g[t].add(s)
    m -= 1


def find(s, t):
    global g
    visited = [0] * n
    queue = deque()
    queue.append(s)

    while queue:
        i = queue.popleft()
        if i == t:
            return True
        for f in g[i]:
            if not visited[f]:
                visited[f] = 1
                queue.append(f)
    return False


q = int(input())
while q:
    s, t = map(int, input().split())
    print('yes' if find(s, t) else 'no')
    q -= 1

Python: import sys
input = lambda: sys.stdin.readline().rstrip()
sys.setrecursionlimit(10**6)
def dfs(g,v,z):
    if vis[v]!=0: return
    else:
        vis[v]=z
        for p in g[v]:
            dfs(g,p,z)
n,m=map(int,input().split())
g=[[] for i in range(n)]
for i in range(m):
    x,y=map(int,input().split())
    g[x].append(y)
    g[y].append(x)
z=0 ; vis=[0]*n
for i in range(n):
    if vis[i]==0:
        z+=1
        dfs(g,i,z)
q=int(input())
for i in range(q):
    x,y=map(int,input().split())
    if vis[x]==vis[y]: print('yes')
    else: print('no')

Python: #coding:utf-8
import sys
sys.setrecursionlimit(10000)
n, r = map(int,input().split())
Q = []
M = [[] for j in range(n)]
for i in range(r):
    i,j = map(int,input().split())
    M[i].append(j)
    M[j].append(i)


def search(person, target):
    data = M[person]
    for per in data:
        if per ==  target:
            global yes
            yes = 1
            return
        if color[per] == "white":
            color[per] = "gray"
            search(per, target)
    color[person] = "black"

num = int(input())
for i in range(num):
    yes = 0
    color = ["white" for j in range(n)]
    person, target = map(int,input().split())
    search(person, target)
    if yes == 0:
        print("no")
    else:
        print("yes")

Python: n, m = map(int, input().split())
g = [set() for _ in range(n)]
group_ids = [0] * n

while m:
    s, t = map(int, input().split())
    g[s].add(t)
    g[t].add(s)
    m -= 1


def search(s, gid):
    global g, group_ids
    queue = set(g[s])
    group_ids[s] = gid

    while queue:
        i = queue.pop()
        if not group_ids[i]:
            group_ids[i] = gid
            queue.update(g[i])


gid = 1
for i in range(n):
    if group_ids[i]:
        continue
    search(i, gid)
    gid += 1

q = int(input())
while q:
    s, t = map(int, input().split())
    gs, gt = group_ids[s], group_ids[t]
    print('yes' if gs and gt and gs == gt else 'no')
    q -= 1

Python: #coding:utf-8
n, r = map(int,input().split())
Q = []
M = [[] for j in range(n)]
for i in range(r):
    i,j = map(int,input().split())
    M[i].append(j)
    M[j].append(i)

def search(person, target):
    Q = []
    Q.append(person)
    color = ["white" for i in range(n)]
    while Q != []:
        u = Q.pop(0)
        if u ==  target:
            print("yes")
            break
        color[u] = "gray"
        data = M[u]
        for v in data:
            if color[v] == "white":
                color[v] = "gray"
                Q.append(v)
        color[u] = "black"
    else:
        print("no")

num = int(input())
for i in range(num):
    person, target = map(int,input().split())
    search(person, target)

Python: # -*- coding: utf-8 -*-
from collections import deque


class LinkedGraph:
    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 check(self, start, goal):
        states = [0] * self.n
        queue = deque([start])

        while queue:
            u = queue.popleft()
            if states[u]:
                continue
            else:
                states[u] = 1

            for v in self.ll[u]:
                if v == goal:
                    print('yes')
                    return
                queue.append(v)

        else:
            print('no')
            return


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

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

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

Python: import sys
readline = sys.stdin.readline
def MAIN():
    n, m = map(int, input().split())
    li = [i for i in range(n)]
    def f(a):
        if li[a] == a:
            return a
        li[a] = f(li[a])
        return li[a]
    def f2(a, b):
        if li[a] == a:
            li[a] = b
            return
        f2(li[a], b)
        li[a] = b
    def solve(a, b):
        if f(a) == f(b):
            return "yes"
        return "no"
    for _ in range(m):
        x, y = map(int, readline().split())
        if f(x) > f(y):
            f2(x, li[y])
        else:
            f2(y, li[x])
    for _ in range(int(input())):
        x, y = map(int, readline().split())
        print(solve(x, y))
MAIN()