网络流算法模板

hdu 4292 (网络流)

 

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
using namespace std;
#define maxn 202
#define INF 0x7fffffff
int flow[maxn][maxn];
int s,e,n;

int fold_folkerson()
{
    int father[maxn];
    int visted[maxn];
    int maxflow[maxn];
    int sumflow=0;
    queue<int> Q;
    int u,i;
    while(1)
    {
        memset(visted,0,sizeof(visted));
        memset(maxflow,0,sizeof(maxflow));
        maxflow[s]=INF;
        Q.push(s);
        visted[s]=1;
        while(!Q.empty())
        {
            u=Q.front();
            Q.pop();
            for(i=1;i<=n;i++)
            {
                if(!visted[i]&&flow[u][i])
                {
                    visted[i]=1;
                    father[i]=u;
                    Q.push(i);
                    maxflow[i]=min(maxflow[u],flow[u][i]);
                }
            }
            if(maxflow[e]>0)
            {
                while(!Q.empty())
                    Q.pop();
                break;
            }
        }
         if(maxflow[e]==0)
                break;
        for(i=e;i!=s;i=father[i])
        {
            flow[father[i]][i]-=maxflow[e];
            flow[i][father[i]]+=maxflow[e];
        }
        sumflow+=maxflow[e];
    }
    return sumflow;
}
int main()
{
    int  m,i,a,b,c;
    while(~scanf("%d%d",&m,&n))
    {
        memset(flow,0,sizeof(flow));
        for(i=0;i<m;i++)
        {
            scanf("%d%d%d",&a,&b,&c);
            flow[a][b]+=c;//这里需要防重边
        }
        s=1;e=n;
        cout<<fold_folkerson()<<endl;
    }
    return 0;
}