Submission #1274341

#	Time	Username	Problem	Language	Result	Execution time	Memory
1274341		dorkikann	Group Photo (JOI21_ho_t3)	C++20	100 / 100	262 ms	134448 KiB

Main

#include <bits/stdc++.h>
using namespace std;

const int N = 5e3 + 5;
const int INF = 1e9;

int DP[N];

int H[N];
int Position[N];

int Help[N][N];
int Help2[N][N];
int Help3[N][N];

void Precalc(int n)
{
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j < i; j++)
            Help[i][j] = Help[i][j-1] + (Position[j] > Position[i]);
    }

    for(int i = n; i >= 1; i--) {
        for(int j = i+1; j <= n; j++) {
            Help2[i][j] = Help2[i][j-1] + (Position[i] > Position[j]);
        }
    }
}

int Find(int a, int b)
{
    int sol = 0;
    sol += Help[b][b-1];
    sol -= Help2[b][a];
    sol += (a-b) - Help2[b][a];
    return sol;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin >> n;

    for(int i = 0; i < n; i++) {
        cin >> H[i];
        Position[H[i]] = i;
    }

    Precalc(n);
    for(int i = 1; i <= n; i++) {
        DP[i] = INF;

        int cnt = 0;
        for(int j = i; j >= 1; j--) {
            cnt += Find(i, j);
            DP[i] = min(DP[i], DP[j-1] + cnt);
        }   
    }
    cout << 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