HDU 1532 Drainage Ditches

http://acm.hdu.edu.cn/showproblem.php?pid=1532

基础题。

#include<iostream> 
#include<cstring>
#include<string>
#include<algorithm>
#include<queue>
using namespace std;

int n, m, flow;
int vis[205];
//路径记录
int pre[205];
//邻接表
int G[205][205];

void Maxflow()
{
    for (;;)
    {
        memset(vis, 0, sizeof(vis));
        queue<int> q;
        q.push(1);
        vis[1] = 1;
        while (!q.empty())
        {
            int x = q.front();
            q.pop();
            //到达终点
            if (x == m)  break;
            for (int i = 1; i <= m; i++)
            {
                if (!vis[i] && G[x][i] > 0)
                {
                    vis[i] = 1;
                    q.push(i);
                    //记录好路径
                    pre[i] = x;
                }
            }
        }
        //没有找到增广路
        if (!vis[m])  break;
        int _min = 1000000;
        for (int i = m; i != 1; i = pre[i])
            _min = min(_min, G[pre[i]][i]);
        for (int i = m; i != 1; i = pre[i])
        {
            G[i][pre[i]] += _min;
            G[pre[i]][i] -= _min;
        }
        flow += _min;
    }
}

int main()
{
    //freopen("D:\txt.txt", "r", stdin);
    while (cin >> n >> m)
    {
        int u, v, w;
        memset(G, 0, sizeof(G));
        for (int i = 0; i < n; i++)
        {
            cin >> u >> v >> w;
            //因为可能存在重边的情况
            G[u][v] += w;
        }
        flow = 0;
        Maxflow();
        cout << flow << endl;
    }
}