首页 > ACM题库 > HDU-杭电 > HDU 1856 More is better-并查集-[解题报告] C++
2013
12-23

HDU 1856 More is better-并查集-[解题报告] C++

More is better

问题描述 :

Mr Wang wants some boys to help him with a project. Because the project is rather complex, the more boys come, the better it will be. Of course there are certain requirements.

Mr Wang selected a room big enough to hold the boys. The boy who are not been chosen has to leave the room immediately. There are 10000000 boys in the room numbered from 1 to 10000000 at the very beginning. After Mr Wang’s selection any two of them who are still in this room should be friends (direct or indirect), or there is only one boy left. Given all the direct friend-pairs, you should decide the best way.

输入:

The first line of the input contains an integer n (0 ≤ n ≤ 100 000) – the number of direct friend-pairs. The following n lines each contains a pair of numbers A and B separated by a single space that suggests A and B are direct friends. (A ≠ B, 1 ≤ A, B ≤ 10000000)

输出:

The output in one line contains exactly one integer equals to the maximum number of boys Mr Wang may keep.

样例输入:

4
1 2
3 4
5 6
1 6
4
1 2
3 4
5 6
7 8

样例输出:

4
2

Hint
A and B are friends(direct or indirect), B and C are friends(direct or indirect), then A and C are also friends(indirect). In the first sample {1,2,5,6} is the result. In the second sample {1,2},{3,4},{5,6},{7,8} are four kinds of answers.

/* THE PROGRAM IS MADE BY PYY */
/*----------------------------------------------------------------------------//
	Copyright (c) 2011 panyanyany All rights reserved.

	URL   : http://acm.hdu.edu.cn/showproblem.php?pid=1856
	Name  : 1856 More is better

	Date  : Monday, August 29, 2011
	Time Stage : half hour

	Result:
4512304	2011-08-29 19:39:07	Accepted	1856
265MS	78584K	1213 B
C++	pyy

4512286	2011-08-29 19:37:01	Wrong Answer	1856
265MS	78584K	1213 B
C++	pyy


Test Data:

Review:
其实也挺简单的,只不过数据有点大,以及res要初始化
为1,因为最少都有一个boy,所以当n=0的时候,res就输出1
//----------------------------------------------------------------------------*/

#include <stdio.h>
#include <string.h>

#define max(a, b) ((a) > (b) ? (a) : (b))

#define MAXSIZE 10000009

int n, res ;
typedef struct tagNODE {
	int cnt, prn ;
} NODE ;

NODE ufSet[MAXSIZE] ;

int find (int x)
{
	int tmp ;
	if (ufSet[x].prn != x)
		ufSet[x].prn = find (ufSet[x].prn) ;
	return ufSet[x].prn ;
}

void merge (int px, int py)
{
	ufSet[py].prn = px ;
	ufSet[px].cnt += ufSet[py].cnt ;
	ufSet[py].cnt = 1 ;

	res = max (res, ufSet[px].cnt) ;
}

int main ()
{
	int i, j ;
	int x, y, px, py ;
	while (scanf ("%d", &n) != EOF)
	{
		res = 1 ;
		for (i = 1 ; i < MAXSIZE ; ++i)
		{
			ufSet[i].prn = i ;
			ufSet[i].cnt = 1 ;
		}
		for (i = 0 ; i < n ; ++i)
		{
			scanf ("%d%d", &x, &y) ;
			px = find (x) ; py = find (y) ;
			if (px != py)
				merge (px, py) ;
		}
		printf ("%d\n", res) ;
	}
	return 0 ;
}

解题报告转自:http://blog.csdn.net/panyanyany/article/details/6730429