【HDOJ】2255 奔小康赚大钱

最大二分图匹配，O(n^3)。

 /* 2255 */
 #include <iostream>
 #include <algorithm>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 using namespace std;

 #define MAXN 305
 #define INF 0x3f3f3f3f

 int w[MAXN][MAXN];
 int link[MAXN];
 int Lx[MAXN], Ly[MAXN];
 int slack[MAXN];
 bool S[MAXN], T[MAXN];
 int n;

 bool dfs(int i) {
     S[i] = true;
     for (int j=; j<=n; ++j) {
         if (T[j])
             continue;
         int tmp = Lx[i]+Ly[j]-w[i][j];
         if (tmp == ) {
             T[j] = true;
             if (!link[j] || dfs(link[j])) {
                 link[j] = i;
                 return true;
             }
         } else {
             slack[j] = min(slack[j], tmp);
         }
     }
     return false;
 }

 void update() {
     int mn = INF;
     for (int i=; i<=n; ++i) if (!T[i]) mn = min(mn, slack[i]);
     for (int i=; i<=n; ++i) {
         if (S[i])    Lx[i] -= mn;
         if (T[i])    Ly[i] += mn;
     }
 }

 void KM() {
     int i, j, k;

     memset(link, , sizeof(link));
     memset(Lx, , sizeof(Lx));
     memset(Ly, , sizeof(Ly));
     for (i=; i<=n; ++i)
         for (j=; j<=n; ++j)
             Lx[i] = max(Lx[i], w[i][j]);
     for (i=; i<=n; ++i) {
         for (;;) {
             memset(S, false, sizeof(S));
             memset(T, false, sizeof(T));
             memset(slack, INF, sizeof(slack));
             if (dfs(i))
                 break;
             else
                 update();
         }
     }
 }

 int main() {
     int i, j, k;
     int ans;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     while (scanf("%d",&n)!=EOF) {
         for (i=; i<=n; ++i)
             for (j=; j<=n; ++j)
                 scanf("%d", &w[i][j]);
         KM();
         for (ans=,i=; i<=n; ++i)
             if (link[i])
                 ans += w[link[i]][i];
         printf("%d\n", ans);
     }

     return ;
 }