2322591_wa.c

北大大牛代码 1240道题的原代码 超级权威

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

int n, m, ans;
int map[501][501];

int bfs()
{
	int i, mark = 0;
	int f, r, p, cnt = 0;
	int pre[501], visited[501];
	int queue[510], C, F[510];

	f = r = -1;
	memset(pre,0,sizeof(pre));
	memset(visited,0,sizeof(visited));
	visited[0] = 1;queue[++f] = 0;pre[0] = -1;
	C = 35000;
	while(f!=r)
	{
		++r;
		p = queue[r];
		for(i = 0; i < n; i++)
			if(map[p][i]&&!visited[i])
			{
				visited[i] = 1;
				queue[++f] = i;
				pre[i] = p;
				F[i] = map[p][i];
				if(i==n-1)
				{	
					mark = 1;
					goto m1;
				}
			}
	}
	m1:;
	if(mark)
	{
		p = n-1;
		while(pre[p]!=-1)
		{
			if(F[p]<C)
				C = F[p];
			p = pre[p];
		}
		p = n-1;
		while(pre[p]!=-1)
		{
			map[pre[p]][p] -= C;
			if(map[pre[p]][p]==0)
				cnt++;
			map[p][pre[p]] += C;
			p = pre[p];
		}
		if(cnt==1)
			ans++;
	}
	return mark;
}

int main()
{
	int i;
	int st, ed, w;

	scanf("%d%d",&n,&m);
	ans = 0;
	memset(map,0,sizeof(map));
	for(i = 0; i < m; i++)
	{
		scanf("%d%d%d",&st,&ed,&w);
		map[st][ed] += w;
	}
	while(bfs());
	printf("%d\n",ans);
	return 1;
}