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: if __name__ == '__main__':
    from sys import stdin
    input = stdin.readline

    from collections import deque, defaultdict
    from copy import deepcopy

    MAX = 100000
    NIL = -1

    # Gはdictで管理する、valueはdeque
    G = defaultdict(lambda: deque())
    color = [NIL]*MAX

    def dfs(r, c):
        S = deque()
        S.append(r)
        color[r] = c
        while S:
            u = S.popleft()
            for v in G[u]:  # Gのvalueはdequeなので、それをvに一つずつ入れていく
                if color[v] == NIL:
                    color[v] = c
                    S.append(v)

    def assign_color():
        id = 1
        for u in range(n):
            if color[u] == NIL:
                dfs(u, id)
                id += 1

    n, m = map(int, input().split())

    for _ in range(m):
        s, t = map(int, input().split())
        G[s].append(t)
        G[t].append(s)

    assign_color()

    q = int(input())
    for _ in range(q):
        s, t = map(int, input().split())
        if color[s] == color[t]:
            print('yes')
        else:
            print('no')

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
        else:
            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()

Python: from queue import deque

n, m = map(int, input().split())
color = [-1 for i in range(n)]
G = deque([[0] * n for i in range(n)])
for i in range(m):
    s, t = map(int, input().split())
    G[s][t] = 1
    G[t][s] = 1

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

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

assginColor()
q = int(input())

for i in range(q):
    s,t = map(int, input().split())
    if color[s] == color[t]:
        print("yes")
    else:
        print("no")

Python: n, m = map(int, input().split())
link = [[] for _ in range(n)]
for _ in range(m):
    u, v = map(int, input().split())
    link[u].append(v)
    link[v].append(u)
group = [-1] * n
gid = 0
for i in range(n):
    if group[i] != -1:
        continue
    stack = [i]
    group[i] = gid
    while stack:
        u = stack.pop()
        for v in link[u]:
            if group[v] == -1:
                group[v] = gid
                stack.append(v)
    gid += 1
q = int(input())
for _ in range(q):
    u, v = map(int, input().split())
    print('yes' if group[u] == group[v] else 'no')

Python: n, m = map(int, input().split())
g = [[] for _ in range(n)]
for i in range(m):
    s, t = map(int, input().split())
    g[s].append(t)
    g[t].append(s)

# dfsで連結成分を求める
r = [0]*n
for i in range(n):
    if r[i] == 0:
        l = [i]
        while len(l) > 0:
            u = l.pop(-1)
            r[u] = i+1
            for v in g[u]:
                if r[v] == 0:
                    l.append(v)

q = int(input())
for i in range(q):
    s, t = map(int, input().split())
    if r[s] == r[t]:
        print("yes")
    else:
        print("no")

Python: 
class UnionFind:
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i in range(self.n) if self.parents[i] < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return "\n".join("{}: {}".format(r, self.members(r)) for r in self.roots())


n,m = map(int,input().split())
tree = UnionFind(n)
for _ in range(m):
    a,b = map(int,input().split())
    tree.union(a,b)

q = int(input())
for i in range(q):
    a,b = map(int,input().split())
    if tree.same(a,b):
        print("yes")
    else:
        print("no")