HDU 1213 How Many Tables (并查集)

How Many Tables

Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d & %I64u

Submit Status Practice HDU 1213

Appoint description: 
System Crawler  (2015-05-25)

Description

Today is Ignatius‘ birthday. He invites a lot of friends. Now it‘s dinner time. Ignatius wants to know how many tables he needs at least. You have to notice that not all the friends know each other, and all the friends do not want to stay with strangers.

One important rule for this problem is that if I tell you A knows B, and B knows C, that means A, B, C know each other, so they can stay in one table.

For example: If I tell you A knows B, B knows C, and D knows E, so A, B, C can stay in one table, and D, E have to stay in the other one. So Ignatius needs 2 tables at least.

Input

The input starts with an integer T(1<=T<=25) which indicate the number of test cases. Then T test cases follow. Each test case starts with two integers N and M(1<=N,M<=1000). N indicates the number of friends, the friends are marked from 1 to N. Then M lines follow. Each line consists of two integers A and B(A!=B), that means friend A and friend B know each other. There will be a blank line between two cases.

Output

For each test case, just output how many tables Ignatius needs at least. Do NOT print any blanks.

Sample Input

2
5 3
1 2
2 3
4 5

5 1
2 5

Sample Output

2
4

还是并查集的模板题。

#include <iostream>
#include <cstdio>
#include <string>
#include <queue>
#include <vector>
#include <map>
#include <algorithm>
#include <cstring>
#include <cctype>
#include <cstdlib>
#include <cmath>
#include <ctime>
using    namespace    std;

const    int    SIZE = 1005;
int    FATHET[SIZE],RANK[SIZE];
int    N,M;

void    ini(int);
int    find_father(int);
void    unite(int,int);
bool    same(int,int);

int    main(void)
{
    int    t;
    int    x,y;

    scanf("%d",&t);
    while(t --)
    {
        scanf("%d%d",&N,&M);
        ini(N);
        while(M --)
        {
            scanf("%d%d",&x,&y);
            unite(x,y);
        }

        bool    vis[SIZE] = {false};
        int    sum = 0;
        for(int i = 1;i <= N;i ++)
            vis[find_father(i)] = true;
        for(int i = 1;i <= N;i ++)
            sum += vis[i];
        printf("%d\n",sum);
    }

    return    0;
}

void    ini(int n)
{
    for(int i = 1;i <= n;i ++)
    {
        FATHET[i] = i;
        RANK[i] = 0;
    }
}

int    find_father(int n)
{
    if(n == FATHET[n])
        return    n;
    return    FATHET[n] = find_father(FATHET[n]);
}

void    unite(int x,int y)
{
    x = find_father(x);
    y = find_father(y);

    if(x == y)
        return    ;
    if(RANK[x] < RANK[y])
        FATHET[x] = y;
    else
    {
        FATHET[y] = x;
        if(RANK[x] == RANK[y])
            RANK[x] ++;
    }
}

bool    same(int x,int y)
{
    return    find_father(x) == find_father(y);
}