bzoj2163

题解：

拆点网络流

然后用总和-最大流

代码：

#include<iostream>
#include<cstring>
#include<cstdio>
#include<queue>
using namespace std;
const int N=;
int ne[N],tot,fi[N],zz[N],z,sl[N],q[N],T,n,m,sum,F[N],dis[N],x,y,cas,ans,f[N];
void jb(int x,int y,int z)
{
    ne[tot]=fi[x];
    fi[x]=tot;
    zz[tot]=y;
    sl[tot++]=z;
    ne[tot]=fi[y];
    fi[y]=tot;
    zz[tot]=x;
    sl[tot++]=;
}
int bfs()
{
    memset(dis,0xff,sizeof dis);
    dis[]=;
    int l=,r=;
    q[]=;
    while (l<r)
     {
         int j=q[++l];
         for (int i=fi[j];i!=-;i=ne[i])
          if (dis[zz[i]]<&&sl[i]>)
           {
               dis[zz[i]]=dis[j]+;
               q[++r]=zz[i];
           }
     }
    if (dis[*n+]>)return ;
    return ;
}
int find(int x,int low)
{
    int b=;
    if (x==*n+)return low;
    for (int i=fi[x];i!=-;i=ne[i])
     if (sl[i]>&&dis[zz[i]]==dis[x]+&&(b=find(zz[i],min(low,sl[i]))))
      {
          sl[i]-=b;
          sl[i^]+=b;
          return b;
      }
    return ;
}
int main()
{
    scanf("%d%d",&n,&m);
    memset(fi,-,sizeof fi);
    for (int i=;i<=n;i++)
     {
        scanf("%d",&F[i]);
        jb(,i+,F[i]);
        jb(i++n,n*+,F[i]);
        sum+=F[i];
     }
    while (m--)
     {
        scanf("%d%d%d",&x,&y,&z);
        jb(x+,+n+y,z);
     }
    int t;
    while (bfs())
     while (t=find(,1e9))ans+=t;
    printf("%d\n",sum-ans);
}