【最大流+模板题】杭电 hdu 3549 Flow Problem

 

 

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

	URL   : http://acm.hdu.edu.cn/showproblem.php?pid=3549
	Name  : 3549 Flow Problem

	Date  : Wednesday, January 4, 2012
	Time Stage : one hour

	Result: 
5228624	2012-01-04 00:37:54	Accepted	3549
62MS	204K	1905 B
C++	pyy


Test Data :

Review :
网络流-最大流模板题……
//----------------------------------------------------------------------------*/

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

using namespace std ;

#define min(x, y)	((x) < (y) ? (x) : (y))

#define INF		0x3f3f3f3f
#define MAXN	20

int		tcase, n, m ;
int		map[MAXN][MAXN], path[MAXN], flow[MAXN] ;

int Make_Point (const int start, const int end)
{
	queue<int>	q ;

	int		t, i ;

	memset (path, 0, sizeof (path)) ;

	flow[start] = INF ;
	path[start] = INF ;
	q.push (start) ;

	while (!q.empty ())
	{
		t = q.front () ;
		q.pop () ;

		if (t == end)
			break ;

		for (i = 1 ; i <= n ; ++i)
		{
			if (map[t][i] && !path[i] && i != start)
			{
				path[i] = t ;
				flow[i] = min (flow[t], map[t][i]) ;
				q.push (i) ;
			}
		}
	}

	if (path[end] == 0)
		return -1 ;
	return flow[end] ;
}

int Edmonds_Kard (const int start, const int end)
{
	int i, j ;
	int incr, step, curr, prev ;

	incr = 0 ;
	while ((step = Make_Point (start, end)) != -1)
	{
		incr += step ;

		curr = end ;			// 倒向追踪
		while (curr != start)
		{
			prev = path[curr] ;
//			printf ("%d, %d\n", curr, prev) ;
			map[prev][curr] -= step ;
			map[curr][prev] += step ;
			curr = prev ;
		}
	}

	return incr ;
}

int main (void)
{
	int	i, j, k, x, y, c ;
	while (~scanf ("%d", &tcase))
	{
		for (k = 1 ; k <= tcase ; ++k)
		{
			memset (map, 0, sizeof (map)) ;
			scanf ("%d%d", &n, &m) ;
			for (i = 1 ; i <= m ; ++i)
			{
				scanf ("%d%d%d", &x, &y, &c) ;
				map[x][y] += c ;
			}
			printf ("Case %d: %d\n", k, Edmonds_Kard (1, n)) ;
		}
	}
	return 0 ;
}