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

 #include <iostream>
 #include <cstring>
 #include <cstdio>
 #include <algorithm>
 #include <cmath>
 using namespace std;
 const int Maxn=;
 int Next[Maxn],F[Maxn],a[Maxn],B[Maxn],Last[Maxn],n,m,Top;
 inline int Min(int x,int y) {return x>y?y:x;}
 int main()
 {
     scanf("%d%d",&n,&m);
     for (int i=;i<=n;i++) scanf("%d",&a[i]);
     int Block=floor(sqrt(n));
     for (int i=;i<=Block;i++) B[i]=;
     for (int i=;i<=n;i++)
     {
         Next[i]=Last[a[i]];
         Last[a[i]]=i;
         for (int j=;j<=Min(Top,Block);j++)
             if (B[j]>Next[i])
             {
                 while (true)
                 {
                     B[j]++;
                     if (B[j]-==Last[a[B[j]-]]) break;
                 }
             }
         if (!Next[i]) Top++;
         F[i]=i;
         for (int j=;j<=Min(Top,Block);j++) F[i]=Min(F[i],F[B[j]-]+j*j);
     }
     printf("%d\n",F[n]);
     return ;
 }

C++