hdu1421 搬寝室

http://acm.hdu.edu.cn/showproblem.php?pid=1421
dfs记忆化搜索写的，没空间优化
 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 
 4 #define N 2013
 5 
 6 int n, k, a[N], dp[N][N];
 7 
 8 int min(int x, int y)
 9 {
10     return x<y? x: y;
11 }
12 
13 int sq(int x)
14 {
15     return x*x;
16 }
17 
18 int dfs(int i, int j)
19 {
20     if(~dp[i][j])
21     {
22         return dp[i][j];
23     }
24     if(i == j)
25     {
26         dp[i][j] = dfs(i-2, j-2)+sq(a[i-1]-a[i]);
27         return dp[i][j];
28     }
29     dp[i][j] = min(dfs(i-2, j-2)+sq(a[i-1]-a[i]), dfs(i-1, j));
30     return dp[i][j];
31 }
32 
33 int cmp(const void *a, const void *b)
34 {
35     return *((int *)a) - *((int *)b);
36 }
37 
38 int main()
39 {
40     int i, j;
41     while(~scanf("%d%d", &n, &k))
42     {
43         k <<= 1;
44         for(i=1; i<=n; i++)
45         {
46             scanf("%d", a+i);
47         }
48         qsort(a+1, n, sizeof(a[0]), cmp);
49         dp[0][0] = 0;
50         for(i=1; i<=n; i++)
51         {
52             dp[i][0] = 0;
53             for(j=2; j<=i; j+=2)
54             {
55                 dp[i][j] = -1;
56             }
57         }
58         printf("%d\n", dfs(n, k));
59     }
60     return 0;
61 }