Go: package main

import (
	"fmt"
)

var n, m int
var g [][]int
var color []int

func main() {
	fmt.Scan(&n, &m)
	g = make([][]int, n) // SNSの関係を表すグラフ
	for i := 0; i < m; i++ {
		var a, b int
		fmt.Scan(&a, &b)
		g[a] = append(g[a], b) // 無向重みなしグラフ
		g[b] = append(g[b], a)
	}
	color = make([]int, n) // 各ノードにつける色
	for i := 0; i < len(color); i++ {
		color[i] = -1 // 初期化しておく
	}
	type query struct {
		s, t int
	}
	var Q int
	fmt.Scan(&Q)
	qs := make([]query, Q)
	for i := 0; i < Q; i++ {
		fmt.Scan(&qs[i].s, &qs[i].t)
	}
	// fmt.Println("n", n, "m", m, "g", g, "Q", Q, "qs", qs)
	// 全ての頂点からdfsする
	id := 1
	for u := 0; u < n; u++ {
		if color[u] == -1 {
			dfs(u, id)
			id++
		}
	}
	// fmt.Println("color", color)
	for i := 0; i < Q; i++ {
		if color[qs[i].s] == color[qs[i].t] {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

func dfs(v, c int) {
	// fmt.Printf("dfs(v %d, c %d) en:\n", v, c)
	color[v] = c
	for _, vv := range g[v] {
		// fmt.Printf("  v %d, g[v] %v, vv %d\n", v, g[v], vv)
		if color[vv] == -1 {
			dfs(vv, c)
		}
	}
}

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

color = [None] * n
S = []
def dfs(r, c):
 S.append(r)
 color[r] = c
 while len(S) != 0:
  u = S.pop()
  for i in SNS[u]:
   if color[i] == None:
    color[i] = c
    S.append(i)
id = 0
for i in range(n):
 if color[i] == None:
  id += 1
  dfs(i, id)

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, raw_input().split())
G = [[0 for i in range(n)] for j in range(n)]

for i in range(m):
    s, t = map(int, raw_input().split())
    G[s][t] = 1
    G[t][s] = 1

for i in range(n):
    for j in range(n):
        for k in range(j+1, n):
            if G[j][k] == 1:
                for l in range(n):
                    if G[k][l] == 1:
                        G[j][l] = 1
                        G[l][j] = 1

q = int(raw_input())
ans = ["no" for i in range(q)]
for i in range(q):
    s, t = map(int, raw_input().split())
    if G[s][t] == 1:
        ans[i] = "yes"
for i in range(q):
    print(ans[i])

Python: def connect(o,s,t):
    global ct
    if color[s]!="white" or ct==1:
        return
    if fr[o][t]==t:
        ct+=1
    color[s]="grey"
    for i in fr[s]:
        if i==-1:
            continue
        elif i==t:
             ct+=1
             break
        else:
            fr[o][i]=i
            fr[i][o]=s
            connect(o,i,t)
            
n,m=map(int,raw_input().split())
fr=[[-1]*n for i in xrange(n)]
for i in xrange(m):
    s,t=map(int,raw_input().split())
    fr[s][t]=t
    fr[t][s]=s
q=input()
for i in xrange(q):
    ct=0
    color=["white"]*n
    s,t=map(int,raw_input().split())
    connect(s,s,t)
    if ct==0:
        print('no')
    else:
        print('yes')
        fr[s][t]=t
        fr[t][s]=s

Python: import sys
sys.setrecursionlimit(10000)
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: n, m = map(int, input().split())

a = [[] for i in range(n)]

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

q = int(input())

from collections import deque
for j in range(q):
    queue = deque()
    memo = [0 for i in range(n)]
    data = list(map(int, input().split()))
    memo[data[0]] = 1
    queue.append(data[0])

    try:
        while len(queue):
            b = queue.popleft()
            for k in a[b]:
                if k == data[1]:
                    print("yes")
                    raise Exception
                if memo[k] == 0:
                    memo[k] = 1
                    queue.append(k)
        print("no")
    except Exception:
        pass

Python: class UnionFind:
    def __init__(self, n: int):
        self.nodes = n
        self.parents = [-1] * n
        self.rank = [0] * n

    # retrun the root of element x
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    # unite the group include element x and group include element y
    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.rank[x] < self.rank[y]:
            self.parents[y] += self.parents[x]
            self.parents[x] = y
        else:
            self.parents[x] += self.parents[y]
            self.parents[y] = x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1

    # get size of the gourp which element x belongs
    def get_size(self, x):
        return -self.parents[self.find(x)]

    # check if element x and element y is same group
    def same(self, x, y):
        return self.find(x) == self.find(y)


n, m = [int(i) for i in input().split()]
union = UnionFind(n)
for _ in range(m):
    s, t = [int(i) for i in input().split()]
    union.unite(s, t)

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

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

import sys


def assign_color():
    _id = 1
    for m in range(vertices_num):
        if vertices_status_list[m] == -1:
            graph_dfs(m, _id)
            _id += 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 = [[] 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")