POJ 1273 Drainage Ditches 最大流

http://poj.org/problem?id=1273
题目大意：
给你N条路径（有重边），和M个点，求以1为源点，M为汇点的最大流。
思路：
第一题最大流问题，直接用Edmonds-Karp算法即可

#include<cstdio>
#include<cstring>
#include<queue>
#include<algorithm>
using namespace std;
const int MAXN = 1<<8;
int map[MAXN][MAXN];
int flow[MAXN];
int pre[MAXN];
int n, m;
int bfs(int s,int t)
{
	memset(pre, -1, sizeof(pre));
	queue<int> q;
	q.push(s);
	pre[s] = 0;
	flow[s] = 0x3ffffff;

	while (!q.empty())
	{
		int cur = q.front();
		q.pop();
		for (int i = 1; i <= m; i++) 
		{
			if (map[cur][i] > 0 && pre[i] == -1)
			{
				flow[i] = min(flow[cur],map[cur][i]);
				pre[i] = cur;
				q.push(i);
			}
		}
	}
	return pre[t] == -1 ? -1 : flow[t];
}


int maxFlow(int s,int t)
{
	int ans = 0;
	int curFlow=0;
	while ((curFlow=bfs(s,t))  !=-1)
	{
		int cur = t;
		while (cur != s)
		{
			map[pre[cur]][cur] -= curFlow;
			map[cur][pre[cur]] += curFlow;
			cur = pre[cur];
		}
		ans += curFlow;
	}
	return ans;
}

int main()
{
	while (~scanf("%d%d", &n, &m))
	{
		memset(map, 0, sizeof(map));
		for (int i = 0; i < n; i++)
		{
			int from, to, val;
			scanf("%d%d%d", &from, &to, &val);
			map[from][to] += val;
		}

		printf("%d\n", maxFlow(1,m));
	}
}