BZOJ 1584 DP

显然序列不能超过sqrt(n)，因为最差情况是每个都独立答案为n

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 #include <algorithm>
 5 #include <cmath>
 6 using namespace std;
 7 const int Maxn=40010;
 8 int Next[Maxn],F[Maxn],a[Maxn],B[Maxn],Last[Maxn],n,m,Top;
 9 inline int Min(int x,int y) {return x>y?y:x;}
10 int main()
11 {
12     scanf("%d%d",&n,&m);
13     for (int i=1;i<=n;i++) scanf("%d",&a[i]);
14     int Block=floor(sqrt(n));
15     for (int i=1;i<=Block;i++) B[i]=1;
16     for (int i=1;i<=n;i++)
17     {
18         Next[i]=Last[a[i]];
19         Last[a[i]]=i;
20         for (int j=1;j<=Min(Top,Block);j++)
21             if (B[j]>Next[i])
22             {
23                 while (true)
24                 {
25                     B[j]++;
26                     if (B[j]-1==Last[a[B[j]-1]]) break;
27                 }
28             }
29         if (!Next[i]) Top++;
30         F[i]=i;
31         for (int j=1;j<=Min(Top,Block);j++) F[i]=Min(F[i],F[B[j]-1]+j*j);
32     }
33     printf("%d\n",F[n]);
34     return 0;
35 }

C++