max_flow模板(POJ 1273)

C++ code:

#include <iostream>

#include <cstdio>

#include <cstring>



using namespace std;



long max_flow();

int M;

long mat[201][201], d[201];



int main()

{

	int N, i, S, E;

	long C;



	while(scanf("%d%d", &N, &M) == 2)

	{

		memset(mat, 0, sizeof(mat));

		mat[0][1] = d[0] = 200000000;

		for(i = 1; i <= N; i++)

		{

			scanf("%d%d%ld", &S, &E, &C);

			mat[S][E] += C;

		}

		printf("%ld\n", max_flow());

	}



	return 0;

}



long max_flow()

{

	long flow[201][201], j;

	int i, pre[201], p, q, t, que[201];



	memset(flow, 0, sizeof(flow));

	for(;;)

	{

		for(i = p = q = t = 0; i <= M; pre[i++] = -1);

		for(; p <= q && pre[M] == -1; t = que[++p])

			for(i = 1; i <= M; i++)

				if((j = mat[t][i] - flow[t][i]) && pre[i] == -1)

				{

					pre[que[++q] = i] = t;

					d[i] = d[t] < j ? d[t] : j;

				}

				else if((j = flow[i][t]) && pre[i] == -1)

				{

					pre[que[++q] = i] = -t;

					d[i] = d[t] < j ? d[t] : j;

				}

		if(p > q)

			break;

		for(i = M; i;)

			if(pre[i] >= 0)

			{

				flow[pre[i]][i] += d[M];

				i = pre[i];

			}

			else if(pre[i] < 0)

			{

				flow[i][-pre[i]] -= d[M];

				i = -pre[i];

			}

	}



	return flow[0][1];

}