WA: csu 1141节能

写着写着越来越觉得是dfs，dp写的不知道哪里出问题了。

 1 # include <stdio.h>
 2 # include <string.h>
 3 
 4 # define INF 1<<30
 5 # define MAXN 1002
 6 
 7 # define MIN(x,y) ((x)<(y) ? (x):(y))
 8 
 9 int n, v;
10 int p[MAXN];
11 int d[MAXN];
12 int vis[MAXN];
13 long long int f[MAXN][MAXN];            /* 子问题f[i][j]：下一个关的是 i 或 j 时，关掉所有灯的最小能耗 */
14 int sp[MAXN][MAXN];            /* sp[i][j]: 所有灯的功率减去 i+1...j-1 号灯的总功率 */
15 
16 long long dp(int i, int j);        /* 记忆化搜索 */
17 
18 int main()
19 {
20     int i, j, k, sumP;
21 
22     while (~scanf("%d%d", &n, &v))
23     {
24         for ( sumP = 0, i = 1; i <= n; ++i)
25         {
26             scanf("%d%d", &d[i], &p[i]);
27             sumP += p[i];
28         }
29 
30         memset(f, 0, sizeof(f));
31         memset(sp, 0, sizeof(sp));
32         memset(vis, 0, sizeof(vis));
33 
34         /* 计算sp[i][j], 其中i<=v, j>=v */
35         for ( i = 1; i < v; ++i)
36         for ( j = v+1; j <= n; ++j)
37         for ( sp[i][j] =  sumP, k = i+1; k < j; ++k)
38             sp[i][j] -= p[k];                
39 
40         printf("%lld\n", dp(v-1, v+1));
41     }
42 
43     return 0;
44 }
45 
46 long long int dp(int i, int j)
47 {
48     long long int t;
49     int k;
50 
51     if ( f[i][j] > 0) return f[i][j];
52 
53     /* 第一次走到第一个灯前并关掉它后，只要关掉右面的 j...n 号灯即可 */
54     if ( i == 0) 
55     {
56         for ( f[i][j] = 0, k = j; k <= n; ++k)
57             f[i][j] += (d[k]-d[1])*p[k];
58         return f[i][j];
59     }
60 
61     /* 第一次走到最后一个灯前并关掉它后，只要关掉右面的 1...i 号灯即可 */
62     if ( j == n+1)
63     {
64         for ( f[i][j] = 0, k = 1; k <= i; ++k)
65             f[i][j] += (d[n]-d[k])*p[k];
66         return f[i][j];
67     }
68     
69     /* 其它分四种情况 */
70     f[i][j] = INF;            
71     if (!vis[i+1]) 
72     {
73         vis[i+1] = 1;
74         if ((t = dp(i-1, j)+(d[i+1]-d[i])*sp[i][j]) < f[i][j]) f[i][j] = t;
75         if ((t = dp(i, j+1)+(d[j]-d[i+1])*sp[i][j]) < f[i][j]) f[i][j] = t;
76         vis[i+1] = 0;
77     }
78     if (!vis[j-1])
79     {
80         vis[j-1] = 1;
81         if ((t = dp(i-1, j)+(d[j-1]-d[i])*sp[i][j]) < f[i][j]) f[i][j] = t;
82         if ((t = dp(i, j+1)+(d[j]-d[j-1])*sp[i][j]) < f[i][j]) f[i][j] = t;
83         vis[j-1] = 0;
84     }
85        
86     return f[i][j];
87 }