Problem:
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Connected Components

Write a program which reads relations in a SNS (Social Network Service), and judges that given pairs of users are reachable each other through the network.

Input

In the first line, two integer $n$ and $m$ are given. $n$ is the number of users in the SNS and $m$ is the number of relations in the SNS. The users in the SNS are identified by IDs $0, 1, ..., n-1$.

In the following $m$ lines, the relations are given. Each relation is given by two integers $s$ and $t$ that represents $s$ and $t$ are friends (and reachable each other).

In the next line, the number of queries $q$ is given. In the following $q$ lines, $q$ queries are given respectively. Each query consists of two integers $s$ and $t$ separated by a space character.

Output

For each query, print "yes" if $t$ is reachable from $s$ through the social network, "no" otherwise.

Constraints

$2 \leq n \leq 100,000$

$0 \leq m \leq 100,000$

$1 \leq q \leq 10,000$

Sample Input

10 9
0 1
0 2
3 4
5 7
5 6
6 7
6 8
7 8
8 9
3
0 1
5 9
1 3

Sample Output

yes
yes
no

Solution in C# (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Aoj.ALDS.Chapter11D
{
    class Program
    {
        public static void Solve()
        {
            int[] n_m = Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
            int n = n_m[0];
            int m = n_m[1];

            var nodes = new List<Node>();
            for (int i = 0; i < n; i++)
            {
                nodes.Add(new Node(i));
            }

            for (int i = 0; i < m; i++)
            {
                int[] ids = Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
                int parentId = Math.Min(ids[0], ids[1]);
                int childId  = Math.Max(ids[0], ids[1]);
                //Console.WriteLine("{0} to {1}", parentId, childId);
                nodes[parentId].Children.Add(nodes[childId]);
            }

            int q = int.Parse(Console.ReadLine());
            for (int i = 0; i < q; i++)
            {
                int[] ids = Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
                int parentId = Math.Min(ids[0], ids[1]);
                int childId  = Math.Max(ids[0], ids[1]);
                // Console.WriteLine("p:{0} c:{1}", parentId, childId);

                // ??¢?´¢
                bool result = Dfs(nodes[parentId], nodes[childId]);
                // Console.WriteLine(result);
                Console.WriteLine("{0}", result ? "yes" : "no");
            }
        }

        public static bool Dfs(Node current, Node target)
        {
            // Console.WriteLine("c:{0}, t:{1}", current.Id, target.Id);
            if (current.Id == target.Id)
            {
                return true;
            }

            // ?¨??????????????????°??????????????????????
            bool result = false;
            foreach (var node in current.Children)
            {
                result = Dfs(node, target);
                if (result) {
                    // ???????????£???????????§????????????
                    break;
                }
            }

            return result || false;
        }

        public static void Main(string[] args)
        {
        	Solve();
        }
    }

    class Node
    {
        // ???????????????
        public int Id { get; set; }

        // ?¨??????????????????°
        public bool Visited { get; set; }

        // ??£??\???????????????(???????????????)
        public List<Node> Children { get; set; }

        public Node(int id)
        {
            Id = id;
            Visited = false;
            Children = new List<Node>();
        }
    }
}