Submission #1225856

#	Time	Username	Problem	Language	Result	Execution time	Memory
1225856		boclobanchat	Group Photo (JOI21_ho_t3)	C++20	100 / 100	268 ms	680 KiB

Main

#include<bits/stdc++.h>
using namespace std;
const int MAXN=5005;
int fen[MAXN],dp[MAXN],A[MAXN],pos[MAXN],pref[MAXN];
void update(int i,int n,int val) { for(;i<=n;i+=i&-i) fen[i]+=val; }
int get(int i) { int ans=0;for(;i;i-=i&-i) ans+=fen[i];return ans; }
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>A[i];
		pos[A[i]]=i,dp[i]=1e9;
	}
	for(int i=1;i<=n;i++)
	{
		int sum=0;
		for(int j=1;j<=n;j++) pref[j]=pref[j-1]+(A[j]>=i);
		for(int j=i;j<=n;j++)
		{
			sum+=pref[pos[j]]-j+i-1+get(pos[j]),dp[j]=min(dp[j],dp[i-1]+sum);
			update(pos[j],n,1);
		}
		for(int j=1;j<=n;j++) fen[j]=0;
	}
	cout<<dp[n];
}

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 32 / 32
• Subtask 4: 20 / 20
• Subtask 5: 36 / 36