Go: // AOJ ALDS1_11_D: http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_11_D

package main

import (
	"bufio"
	"container/list"
	"fmt"
	"os"
	"strconv"
)

var nocolor = -1

type graph struct {
	graph  [][]int
	colors []int
}

func nextInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

func newGraph(nodeNum int) *graph {
	colors := make([]int, nodeNum)
	g := make([][]int, nodeNum)
	for i := 0; i < nodeNum; i++ {
		g[i] = []int{}
		colors[i] = nocolor
	}

	return &graph{g, colors}
}

func constructGraph(sc *bufio.Scanner) *graph {
	usersNum := nextInt(sc)
	linkNum := nextInt(sc)

	g := newGraph(usersNum)
	for i := 0; i < linkNum; i++ {
		u := nextInt(sc) // node
		l := nextInt(sc) // link node
		// edge each other
		g.graph[u] = append(g.graph[u], l)
		g.graph[l] = append(g.graph[l], u)
	}
	return g
}

func (g *graph) dfs(r, color int) {
	g.colors[r] = color

	stack := list.New()
	stack.PushFront(r)

	for stack.Len() > 0 {
		v := stack.Remove(stack.Front()).(int)
		for _, u := range g.graph[v] {
			if g.colors[u] == nocolor {
				g.colors[u] = color
				stack.PushFront(u)
			}
		}
	}
}

func (g *graph) assignColor() {
	color := 1
	for u := 0; u < len(g.graph); u++ {
		if g.colors[u] == nocolor {
			g.dfs(u, color)
			color++
		}
	}
}

func (g *graph) isLink(s, t int) bool {
	return g.colors[s] == g.colors[t]
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	// construct graph and friendly colors
	g := constructGraph(sc)
	g.assignColor()

	// judge link
	q := nextInt(sc)
	for i := 0; i < q; i++ {
		s := nextInt(sc)
		t := nextInt(sc)

		if g.isLink(s, t) {
			fmt.Println("yes")
		} else {
			fmt.Println("no")
		}
	}
}

C++: #include <iostream>
#include <vector>
#include <queue>
using namespace std;
int main(){
  int n,m,t1,t2,c[100000]={}; vector <int> g[100000];
  cin>>n>>m;
  for(int i=0;i<m;i++){
    cin>>t1>>t2;
    g[t1].push_back(t2);
    g[t2].push_back(t1);
  }
  int l;cin>>l;
  for(int i=0;i<n;i++) if(!c[i]){
      queue <int> q; bool f[100000]={};
      q.push(i);f[i]=true;c[i]=i+1;
      for(;!q.empty();){
        for(int j=0;j<g[q.front()].size();j++){
          int v=g[q.front()][j];
          if(!f[v]){
            f[v]=true;c[v]=i+1;
            q.push(v);
          }
	}
          q.pop();
      }
    }
  for(int i=0;i<l;i++){
    cin>>t1>>t2;
    if(c[t1]==c[t2]) cout<<"yes"<<endl;
    else cout<<"no"<<endl;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP0(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define REP1(i,n) for(int i=1, i##_len=(n); i<=i##_len; ++i)
#define RREP0(i,n) for(int i=n-1; i>=0; --i)
#define RREP1(i,n) for(int i=n; i>=1; --i)

#define SORT(c) sort((c).begin(),(c).end())
#define whole(f,x,...) ([&](decltype((x)) whole) { return (f)(begin(whole), end(whole), ## __VA_ARGS__); })(x)
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define CLR(a) memset((a), 0 ,sizeof(a))

inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

typedef long long LL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;

const int INTINF = 2147483647;
const LL LLINF = 9223372036854775807;
const double EPS = 1e-10;
const double PI  = acos(-1.0);
const int MAX = 100000;
const int NIL = -1;

int gcd(int a,int b){return b?gcd(b,a%b):a;}
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
int n,m,q;
VI G[MAX];
int color[MAX];


void dfs(int r, int c) {
  stack<int> S;
  S.push(r);
  color[r] = c;
  while ( !S.empty() ) {
    int u = S.top(); S.pop();
    REP0( i, G[u].size() ){
      int v = G[u][i];
      if ( color[v] == NIL ) {
        color[v] = c;
        S.push(v);
      }
    }
  }
}


void assignColor(){
  int id=1;
  REP0(i,n) color[i]=NIL;
  REP0(u,n) if (color[u]==NIL) dfs(u, id++);
  //連結成分ごとにdfsしcoloring
}


void input(){
  std::cin >> n >> m;
  int s,t;
  REP0(i,m){
    std::cin >> s >> t;
    G[s].PB(t);
    G[t].PB(s);
  }
}


void output() {
  std::cin >> q; int s,t;
  REP0(i,q){
    std::cin >> s >> t;
    if (color[s]==color[t]) {
      std::cout << "yes" << '\n';
    }else{
      std::cout << "no" << '\n';
    }
  }
}


int main(int argc, char const *argv[]) {
  input();
  assignColor();
  output();
  return 0;
}

C++: #include <iostream>
#include <vector>
#include <stack>
#define MAX 100005
#define NIL -1 
using namespace std;

int color[MAX];
int n,m,s,t,q;
vector<int> G[MAX];

void dfs(int x, int y) {
	stack<int> S;
	S.push(x);
	color[x]=y;
	while(!S.empty()) {
		int tmp=S.top();
		S.pop();
		for(int i=0;i<G[tmp].size();i++) {
			int l=G[tmp][i];
			if(color[l]==NIL) {
				color[l]=y;
				S.push(l);
			}
		}
	}
}

void assigncolor() {
	int num=0;
	for(int i=0;i<n;i++) color[i]=NIL;
	for(int i=0;i<n;i++) {
		if(color[i]==NIL) dfs(i,num++);
	}
}

int main() {
	int i,j;
	scanf("%d %d",&n,&m);
	for(i=0;i<m;i++) {
		scanf("%d %d",&s,&t);
		G[s].push_back(t);
		G[t].push_back(s);
	}
	
	assigncolor();
	
	scanf("%d",&q);
	for(i=0;i<q;i++) {
		scanf("%d %d",&s,&t);
		if(color[s]==color[t]) printf("yes\n");
		else printf("no\n");
	}
	
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;

const int N = 100000;
const int NIL = -1;

int n;
vector<int> G[N];
int color[N];

void dfs(int r, int c){
    stack<int> S;
    S.push(r);
    color[r] = c;

    while(!S.empty()){
        int x = S.top(); S.pop();
        for(int i = 0; i < G[x].size(); i++){
            int v = G[x][i];
            if(color[v] == NIL){
                color[v] = c;
                S.push(v);
            }
        }
    }
}

void solve(){
    int id = 1;
    for(int i = 0; i < n; i++)  color[i] = NIL;
    for(int u = 0; u < n; u++){
        if(color[u] == NIL) dfs(u, id++);
    }
}

int main(){
    int q, s, t;
    cin >> n >> q;

    while(q-- > 0){
        cin >> s >> t;
        G[s].push_back(t);
        G[t].push_back(s);
    }

    solve();

    cin >> q;
    while(q-- > 0){
        cin >> s >> t;
        if(color[s] == color[t])    cout << "yes" << endl;
        else                        cout << "no" << endl;
    }

    return 0;
}

C++: #include <vector>
#include <iostream>
using namespace std;
int n, q, x, y; int group[100000]; vector<int> f[100000];
int main() {
	scanf("%d%d", &n, &m);
	for(int i = 0; i < n; i++) group[i] = i, f[i].push_back(i);
	for(int i = 0; i < m; i++) {
		scanf("%d%d", &x, &y);
		if(group[x] == group[y]) continue;
		x = group[x], y = group[y];
		if(f[y].size() > f[x].size()) swap(x, y);
		for(int j = f[y].size() - 1; j >= 0; j--) {
			group[f[y][j]] = group[x];
			f[x].push_back(f[y][j]);
			f[y].pop_back();
		}
	}
	scanf("%d", &q);
	for(int i = 0; i < q; i++) {
		scanf("%d%d", &x, &y);
		printf("%s\n", group[x] == group[y] ? "yes" : "no");
	}
	return 0;
}

C++: #include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#define Lens 1005

using namespace std;
int n, m, q;
queue<int> Q;
vector<int> A[Lens];
char c[Lens], d[Lens];
int way[Lens][Lens];

void bns(int k)
{
	Q.push(k);
	c[k] = 'g';
	while (!Q.empty())
	{
		k = Q.front();
		Q.pop();
		c[k] = 'g';
		for (int i = 0; i < A[k].size(); i++)
		{
			int tmp = A[k][i];
			if (c[tmp] == 'w')
			{
				Q.push(tmp);
			}
		}
	}
}

int main()
{
	cin >> n >> m;
	for (int i = 0; i < m; i++)
	{
		int s, t;
		cin >> s >> t;
		                                    c[s] = c[t] = 'w';
		A[s].push_back(t);
		A[t].push_back(s);
	}
	cin >> q;
	for (int i = 0; i < q; i++)
	{
		int s, t;
		cin >> s >> t;
		bns(s);
		if (c[s]==c[t])
			cout << "yes" << endl;
		else
			cout << "no" << endl;
	}
	return 0;
}