【HDOJ】2255 奔小康赚大钱

最大二分图匹配，O(n^3).

 1 /* 2255 */
 2 #include <iostream>
 3 #include <algorithm>
 4 #include <cstdio>
 5 #include <cstring>
 6 #include <cstdlib>
 7 using namespace std;
 8
 9 #define MAXN 305
10 #define INF 0xfffffff
11
12 int w[MAXN][MAXN];
13 int link[MAXN];
14 int Lx[MAXN], Ly[MAXN];
15 int slack;
16 bool S[MAXN], T[MAXN];
17 int n;
18
19 bool dfs(int i) {
20     S[i] = true;
21     for (int j=1; j<=n; ++j) {
22         if (T[j])
23             continue;
24         int tmp = Lx[i]+Ly[j]-w[i][j];
25         if (tmp == 0) {
26             T[j] = true;
27             if (!link[j] || dfs(link[j])) {
28                 link[j] = i;
29                 return true;
30             }
31         } else if (slack > tmp) {
32             slack = tmp;
33         }
34     }
35     return false;
36 }
37
38 void update() {
39     for (int i=1; i<=n; ++i) {
40         if (S[i])    Lx[i] -= slack;
41         if (T[i])    Ly[i] += slack;
42     }
43 }
44
45 void KM() {
46     int i, j, k;
47
48     memset(link, 0, sizeof(link));
49     memset(Lx, 0, sizeof(Lx));
50     memset(Ly, 0, sizeof(Ly));
51     for (i=1; i<=n; ++i)
52         for (j=1; j<=n; ++j)
53             Lx[i] = max(Lx[i], w[i][j]);
54     for (i=1; i<=n; ++i) {
55         for (;;) {
56             memset(S, false, sizeof(S));
57             memset(T, false, sizeof(T));
58             slack = INF;
59             if (dfs(i))
60                 break;
61             else
62                 update();
63         }
64     }
65 }
66
67 int main() {
68     int i, j, k;
69     int ans;
70
71     #ifndef ONLINE_JUDGE
72         freopen("data.in", "r", stdin);
73     #endif
74
75     while (scanf("%d",&n)!=EOF) {
76         for (i=1; i<=n; ++i)
77             for (j=1; j<=n; ++j)
78                 scanf("%d", &w[i][j]);
79         KM();
80         for (ans=0,i=1; i<=n; ++i)
81             if (link[i])
82                 ans += w[link[i]][i];
83         printf("%d\n", ans);
84     }
85
86     return 0;
87 }