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=40010;
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=1;i<=n;i++) scanf("%d",&a[i]); 
    int Block=floor(sqrt(n));
    for (int i=1;i<=Block;i++) B[i]=1;
    for (int i=1;i<=n;i++)
    {
        Next[i]=Last[a[i]];
        Last[a[i]]=i;
        for (int j=1;j<=Min(Top,Block);j++)
            if (B[j]>Next[i])
            {
                while (true)
                {
                    B[j]++;
                    if (B[j]-1==Last[a[B[j]-1]]) break;
                }
            }
        if (!Next[i]) Top++;
        F[i]=i;
        for (int j=1;j<=Min(Top,Block);j++) F[i]=Min(F[i],F[B[j]-1]+j*j);
    }
    printf("%d
",F[n]);
    return 0;
}