hdu 2426 Interesting Housing Problem 最大权匹配KM算法

  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstring>
  4 #include<cstdlib>
  5 #include<cmath>
  6 #include<algorithm>
  7 #define inf 0x7fffffff
  8 using namespace std;
  9 const int maxn=500+10;
 10 
 11 int n,m;
 12 int lx[maxn],ly[maxn],visx[maxn],visy[maxn];
 13 int link[maxn],slack[maxn],w[maxn][maxn];
 14 
 15 int dfs(int x)
 16 {
 17     visx[x]=1;
 18     for (int y=1 ;y<=m ;y++) if (w[x][y]!=-1)
 19     {
 20         if (visy[y]) continue;
 21         int t=lx[x]+ly[y]-w[x][y];
 22         if (t==0)
 23         {
 24             visy[y]=1;
 25             if (link[y]==-1 || dfs(link[y]))
 26             {
 27                 link[y]=x;
 28                 return 1;
 29             }
 30         }
 31         else if (slack[y]>t) slack[y]=t;
 32     }
 33     return 0;
 34 }
 35 
 36 int KM()
 37 {
 38     memset(link,-1,sizeof(link));
 39     memset(ly,0,sizeof(ly));
 40     for (int x=1 ;x<=n ;x++)
 41     {
 42         lx[x]=-inf;
 43         for (int y=1 ;y<=m ;y++)
 44             lx[x]=max(lx[x],w[x][y]);
 45     }
 46     for (int x=1 ;x<=n ;x++)
 47     {
 48         for (int i=1 ;i<=m ;i++) slack[i]=inf;
 49         int flag=0;
 50         for (int i=1 ;i<=m ;i++) if (w[x][i]!=-1) flag=1;
 51         while (flag)
 52         {
 53             memset(visx,0,sizeof(visx));
 54             memset(visy,0,sizeof(visy));
 55             if (dfs(x)) break;
 56             int d=inf;
 57             for (int i=1 ;i<=m ;i++)
 58                 if (!visy[i] && d>slack[i]) d=slack[i];
 59             for (int i=1 ;i<=n ;i++)
 60                 if (visx[i]) lx[i] -= d;
 61             for (int i=1 ;i<=m ;i++)
 62             {
 63                 if (visy[i]) ly[i] += d;
 64                 else slack[i] -= d;
 65             }
 66         }
 67     }
 68     int ans=0;
 69     int vis[maxn];
 70     memset(vis,0,sizeof(vis));
 71     for (int i=1 ;i<=m ;i++)
 72     {
 73         if (link[i]!=-1)
 74         {
 75             ans += w[link[i] ][i];
 76             vis[link[i] ]=1;
 77         }
 78     }
 79     int i=1;
 80     for (i=1 ;i<=n ;i++)
 81         if (vis[i]==0) return -1;
 82     return ans;
 83 }
 84 
 85 int main()
 86 {
 87     int e;
 88     int ncase=1;
 89     while (scanf("%d%d%d",&n,&m,&e)!=EOF)
 90     {
 91         memset(w,-1,sizeof(w));
 92         int a,b,c;
 93         for (int i=0 ;i<e ;i++)
 94         {
 95             scanf("%d%d%d",&a,&b,&c);
 96             a++ ;b++ ;
 97             if (c>=0) w[a][b]=c;
 98         }
 99         printf("Case %d: %d\n",ncase++,KM());
100     }
101     return 0;
102 }