hdu 2255 奔小康赚大钱 (km算法模板)

题目链接：

　　http://acm.hdu.edu.cn/showproblem.php?pid=2255

解题思路：

　　了解km算法以后，就可以直接套用km算法，km算法：完备匹配下的最大权匹配，

代码：

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <iostream>
 4 #include <algorithm>
 5 using namespace std;
 6
 7 #define maxn 310
 8 #define INF 0x3f3f3f3f
 9 int map[maxn][maxn], used[maxn], s[maxn], n, m;
10 int lx[maxn], ly[maxn], visx[maxn], visy[maxn];
11
12 int find (int x)
13 {//匈牙利算法，增广路
14     visx[x] = 1;
15     for (int i=1; i<=n; i++)
16     {
17         if (!visy[i] && lx[x] + ly[i] == map[x][i])
18         {
19             visy[i] = 1;
20             if (!used[i] || find(used[i]))
21             {
22                 used[i] = x;
23                 return 1;
24             }
25         }
26         else
27             s[i] = min (s[i], lx[x]+ly[i]-map[x][i]);
28     }
29     return 0;
30 }
31
32 int KM ()
33 {
34     memset (lx, 0, sizeof(lx));
35     memset (ly, 0, sizeof(ly));
36     memset (used, 0, sizeof(used));
37     for (int i=1; i<=n; i++)
38         for (int j=1; j<=n; j++)
39             lx[i] = max (lx[i], map[i][j]);
40     for (int i=1; i<=n; i++)
41     {
42         for (int j=1; j<=n; j++)
43             s[j] = INF;
44
45         while (1)
46         {
47             memset (visx, 0, sizeof(visx));
48             memset (visy, 0, sizeof(visy));
49
50             if (find (i))
51                 break;
52             int num = INF;
53             for (int j=1; j<=n; j++)
54                 if (!visy[j])
55                     num = min (num, s[j]);
56             for (int j=1; j<=n; j++)
57             {
58                 if (visx[j])
59                     lx[j] -= num;
60                 if (visy[j])
61                     ly[j] += num;
62                 else
63                     s[j] -= num;
64             }
65         }
66     }
67     int res = 0;
68     for (int j=1; j<=n; j++)
69         res += map[used[j]][j];
70     return res;
71 }
72 int main ()
73 {
74     while (scanf ("%d", &n) != EOF)
75     {
76         for (int i=1; i<=n; i++)
77             for (int j=1; j<=n; j++)
78                 scanf ("%d", &map[i][j]);
79         printf ("%d\n", KM());
80     }
81     return 0;
82 }