【KM算法】HDU2255-奔小康赚大钱

KM算法的裸体。O（n^4）的模板，实际上在增广路径的时候依然有冗余，可以用bfs优化到O(n^3)。

 #include <iostream>
 #include <cstdio>
 #include <cmath>
 #include <cstring>
 #include <cstdlib>
 #include <algorithm>
 using namespace std;
 const int MAXN=+;
 const int INF=0x7fffffff;
 int n,m;
 int w[MAXN][MAXN];
 int x[MAXN],y[MAXN];
 int visx[MAXN],visy[MAXN],slack[MAXN];
 int lk[MAXN];

 int dfs(int u)
 {
     visx[u]=;
     for (int i=;i<=n;i++)
     {
         int wt=x[u]+y[i]-w[u][i];
         if (!visy[i] && wt==)
         {
             visy[i]=;
             if (lk[i]==- || dfs(lk[i]))
             {
                 lk[i]=u;
                 return ;
             }
         }
         else if (slack[i]>wt) slack[i]=wt;
     }
     return ;
 }

 int KM()
 {
     memset(lk,-,sizeof(lk));
     for (int i=;i<=n;i++)
     {
         y[i]=;
         x[i]=-INF;
         for (int j=;j<=n;j++) x[i]=max(x[i],w[i][j]);
     }
     for (int i=;i<=n;i++)
     {
         memset(visx,,sizeof(visx));
         memset(visy,,sizeof(visy));
         memset(slack,,sizeof(slack));
         while (!dfs(i))
         {
             int delta=INF;
             for (int j=;j<=n;j++)
                 if (!visy[j] && slack[j]<delta) delta=slack[j];
             for (int j=;j<=n;j++)
             {
                 if (visx[j])
                 {
                     x[j]-=delta;
                     visx[j]=;
                 }
                 if (visy[j])
                 {
                     y[j]+=delta;
                     visy[j]=;
                 }
             }
         }
     }
     int ret=;
     for (int i=;i<=n;i++) ret+=x[i]+y[i];
     return ret;
 }

 void init()
 {
     memset(w,,sizeof(w));
     for (int i=;i<=n;i++)
     {
         for (int j=;j<=n;j++)
             scanf("%d",&w[i][j]);
     }
 }

 int main()
 {
     while (~scanf("%d",&n))
     {
         init();
         printf("%d\n",KM());
     }
     return ;
 }