Submission #389638

#	Time	Username	Problem	Language	Result	Execution time	Memory
389638		mariowong	Group Photo (JOI21_ho_t3)	C++14	100 / 100	313 ms	67572 KiB

Main

#include <bits/stdc++.h>

using namespace std;


int dp[5005],a[5005],pos[5005],n,ans,ps[5005][5005];
int main(){
	ios::sync_with_stdio(false);
	cin >> n;
	for (int i=1;i<=n;i++){
		cin >> a[i];
		pos[a[i]]=i;
	}
	for (int i=1;i<=n;i++){
		for (int j=i+1;j<=n;j++){
			if (pos[i] > pos[j])
			ans++;
		}
	}
	for (int i=2;i<=n;i++){
		for (int j=1;j+i-1<=n;j++){
			ps[i][j]=ps[i-1][j]+ps[i-1][j+1]-ps[i-2][j+1];
			if (pos[j] > pos[j+i-1])
			ps[i][j]++;
		}
	}
	for (int i=1;i<=n;i++){
		for (int j=1;j<=i;j++){
			dp[i]=min(dp[i],dp[j-1]-(ps[i-j+1][j]-(i-j+1)*(i-j)/2+ps[i-j+1][j]));
		}
	}
	cout << ans+dp[n] << '\n';
	return 0;
}

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