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

global visited 
visited = [0 for _ in range(n)]

def input_graph(m):
  for _ in range(m):
    u, v = map(int, input().split())
    graph[u].append(v)
    graph[v].append(u)

def dfs(node_id):
  
  for ad_node in graph[node_id]:
    if visited[ad_node] == 1:
      continue
    visited[ad_node] = 1
    dfs(ad_node)

if __name__ == "__main__":
  input_graph(m)
  q_num = int(input())
  for _ in range(q_num):
    visited = [0 for _ in range(n)]
    s, t = map(int, input().split())
    dfs(s)
    if visited[t]:
      print("yes")
    else:
      print("no")

Python: def bfs(graph, start, goal, connection):
    visited = {start: None}
    unvisited = [start]
    while unvisited:
        now = unvisited[0]
        if now == goal or (1000000*now + goal) in connection:
            connection[1000000*start + goal] = 1
            return "yes"
        unvisited = unvisited[1:]
        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 = [None]*n
c = {}

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

q = int(input())

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

Python: #!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys


def assign_color():
    _color = 1
    for m in range(vertices_num):
        if vertices_status_list[m] == -1:
            graph_dfs(m, _color)
            _color += 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 = tuple([[] for _ in range(vertices_num)])
    vertices_status_list = [-1] * vertices_num

    for relation in relation_info:
        key, value = map(int, relation.split())
        adj_list[key].append(value)
        adj_list[value].append(key)

    assign_color()

    # print(adj_list)
    for question in question_list:
        start, target = map(int, question.split())
        if vertices_status_list[start] == vertices_status_list[target]:
            print("yes")
        else:
            print("no")

Python: def DFS(s):
    flag[s] = 1
    group[j] += s
    for i in range(n):
        if G[s] == i and flag[i] == 0:
                DFS(i)
 

n, m = map(int, input().split())
G = [[] for j in range(n)]
for i in range(m):
    s, t = map(int, input().split())
    G[s] += t
    G[t] += s

flag = [0 for i in range(n)]
group = []
j = 0
for i in range(n):
    if flag[i] == 0:
        group.append([])
        DFS(i)
        j += 1

q = int(input())
ans = ["no" for i in range(q)]
for i in range(q):
    s, t = map(int, input().split())
    for j in range(len(group)):
        if s in group[j] and t in gruop[j]:
            ans[i] = "yes"
for i in range(q):
    print(ans[i])

Python: import sys
sys.setrecursionlimit(10000)

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")