【bzoj5125】[Lydsy12月赛]小Q的书架 dp优化

#include<bits/stdc++.h>
#define ll long long
#define inf 1000000000
#define mod 65537
using namespace std;
inline int read()
{
int x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
int n,t[40005],L=1,R=0,ans,a[40005],dp[40005],DP[40005],k;
inline void add(int x,int y)
{
for (;x<=n;x+=x&-x)t[x]+=y;
}
inline int query(int x)
{
int ans=0;
for (;x;x-=x&-x)ans+=t[x];
return ans;
}
inline void Move(int l,int r)
{
while (L<l){add(a[L],-1);ans-=query(a[L]-1);L++;}
while (L>l){L--;add(a[L],1);ans+=query(a[L]-1);}
while (R<r){R++;add(a[R],1);ans+=(R-L+1)-query(a[R]);}
while (R>r){add(a[R],-1);ans-=(R-L)-query(a[R]);R--;}
}
void solve(int l,int r,int L,int R)
{
if (l>r) return;
int mid=(l+r)>>1,MIN=1600000005,p=L;
for (int i=L;i<=R&&i<mid;i++)
{
Move(i+1,mid);
if (dp[i]+ans<MIN){MIN=dp[i]+ans;p=i;}
}
DP[mid]=MIN;
solve(l,mid-1,L,p);
solve(mid+1,r,p,R);
}
int main()
{
n=read();k=read();for (int i=1;i<=n;i++) a[i]=read();
for (int i=1;i<=n;i++)
{
Move(1,i);dp[i]=ans;
}
for (int i=1;i<k;i++)
{
solve(1,n,1,n);
for (int i=1;i<=n;i++) dp[i]=DP[i];
}
printf("%d",dp
);
return 0;
}