poj 1459 Power Network 最大流

      这题没有给出源点和汇点，需要自己添加。

       添加一个与所有类型为p的点相连的源点和一个与所有类型为c的点相连的汇点，边的值为题目给的，而不是INF。

       例外这题输入比较麻烦。

 

#include <iostream>
#include <queue>
using namespace std;

const int N = 505;
const int INF = 1000000000;

int cap[N][N];
int flow[N][N];
int min_flow[N];
int pre[N];
int n, np, nc, m;

int max_flow(int source, int sink)
{
	memset(flow, 0, sizeof(flow));
	
	int u;
	int ans = 0;

	while (1)
	{
		memset(pre, -1, sizeof(pre));
		queue<int> Q;
		min_flow[source] = INF;
		Q.push(source);

		while (!Q.empty())
		{
			u = Q.front();
			Q.pop();

			if (u == sink)	break;
			for (int i = 1; i <= sink; i++)
			{
				if (pre[i] < 0 && cap[u][i] > flow[u][i])
				{
					pre[i] = u;
					min_flow[i] = min(min_flow[u], cap[u][i] - flow[u][i]);
					Q.push(i);
				}
			}
		}

		if (pre[sink] < 0) break;

		for (int v = sink; v != source; v = pre[v])
		{
			int u = pre[v];
			flow[u][v] += min_flow[sink];
			flow[v][u] -= min_flow[sink];
		}

		ans += min_flow[sink];
	}

	return ans;
}

int main()
{
	int x, y, z;
	char c;

	while (scanf("%d%d%d%d", &n, &np, &nc, &m) != EOF)
	{
		memset(cap, 0, sizeof(cap));

		for (int i = 0; i < m; i++)
		{
			while (c = getchar())
			{
				if (c == '(')
					break;
			}
			scanf("%d,%d)%d", &x, &y, &z);
			
			cap[x+1][y+1] = z;
		}

		for (int i = 0; i < np; i++)
		{
			while (c = getchar())
			{
				if (c == '(')
					break;
			}
			scanf("%d)%d", &x, &z);
					
			cap[0][x+1] = z;
		}

		for (int i = 0; i < nc; i++)
		{
			while (c = getchar())
			{
				if (c == '(')
					break;
			}
			scanf("%d)%d", &x, &z);
			
			cap[x+1][n+1] = z;
		}

		printf("%d\n", max_flow(0, n+1));
	}
	return 0;
}