hdu3488

题解：

首先把每一个点拆到两边

然后做KM求最大

吧没一条边相反即可

代码：

#include<cstdio>
#include<cmath>
#include<algorithm>
#include<cstring>
using namespace std;
const int N=;
int a[N][N],z;
int visr[N],T,x,y,exl[N],exr[N],visl[N],match[N],slack[N],n,m;
int dfs(int x)
{
    visl[x]=;
    for (int i=;i<=n;i++)
     if (!visr[i])
      {
          int k=exl[x]+exr[i]-a[x][i];
          if (k==)
           {
               visr[i]=;
               if (!match[i]||dfs(match[i]))
                {
                    match[i]=x;
                    return ;
                }
           }
          else slack[i]=min(slack[i],k);
      }
    return ;
}
int read()
{
    char c;int x=;
    for (;c<''||c>'';c=getchar());
    for (;c>=''&&c<='';c=getchar())x=x*+c-;
    return x;
}
int main()
{
    T=read();
    while (T--)
     {
         n=read();m=read();
         for (int i=;i<=n;i++)
          for (int j=;j<=n;j++)a[i][j]=-(n*+);
         while (m--)
          {
              x=read();y=read();z=read();
              a[x][y]=max(-z,a[x][y]);
          }
         for (int i=;i<=n;i++)exl[i]=-(n*+);
         memset(exr,,sizeof exr);
        for (int i=;i<=n;i++)
         for (int j=;j<=n;j++)exl[i]=max(exl[i],a[i][j]);
        memset(match,,sizeof match);
         for (int i=;i<=n;i++)
         {
              memset(slack,0x3f,sizeof slack);
              while ()
               {
                   memset(visl,,sizeof visl);
                   memset(visr,,sizeof visr);
                   if (dfs(i))break;
                   int d=1e9;
                   for (int j=;j<=n;j++)
                    if (!visr[j])d=min(d,slack[j]);
                   for (int j=;j<=n;j++)
                 {
                     if (visl[j])exl[j]-=d;
                     if (visr[j])exr[j]+=d;
                     else slack[j]-=d;
                 }
               }
         }
        int ans=;
        for (int i=;i<=n;i++)
         ans+=a[match[i]][i];
        printf("%d\n",-ans);
     }
}