poj 1273 Drainage Ditches

#include<iostream>            //网络流
#include<queue>
using namespace std;
#define inf 0x7fffffff
int flow[202][202],cap[202][202],a[202],p[202],s,t,f;
int main()
{
    int n,m;
    while(cin>>n>>m)
    {
        memset(cap,0,sizeof(cap));
        int si,ei,ci;
        while(n--)
        {
            cin>>si>>ei>>ci;
            cap[si][ei]+=ci;    //边是有向的,而且可能重复
        }
        s=1;t=m;
        queue<int> col;
        memset(flow,0,sizeof(flow));
        f=0;
        while(1)
        {
            memset(a,0,sizeof(a));
            a[s]=inf;
            col.push(s);
            while(!col.empty())
            {
                int u=col.front();col.pop();
                for(int i=1;i<=m;++i)
                    if(!a[i]&&cap[u][i]>flow[u][i])
                    {
                        a[i]=min(a[u],cap[u][i]-flow[u][i]);
                        p[i]=u;
                        col.push(i);
                    }
            }
            if(a[t]==0)
                break;
            for(int i=t;i!=s;i=p[i])
                flow[p[i]][i]+=a[t],flow[i][p[i]]-=a[t];
            f+=a[t];
        }
        cout<<f<<endl;
    }
    return 0;
}