Submission #534461

#	Time	Username	Problem	Language	Result	Execution time	Memory
534461		someone	Group Photo (JOI21_ho_t3)	C++14	100 / 100	419 ms	197848 KiB

Main

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

const int N = 5e3 + 42, INF = 1e18;

int n, a[N], pos[N], val[N], inv[N][N];

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    
    cin >> n;
    for(int i = 0; i < n; i++)
        cin >> a[i];
    for(int i = 0; i < n; i++)
        pos[a[i]-1] = i;
    for(int i = 0; i < n; i++)
        for(int j = i+1; j < n; j++)
            if(pos[i] > pos[j])
                inv[i+1][j+1] = 1;
    
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++)
            inv[i][j] += inv[i-1][j] + inv[i][j-1] - inv[i-1][j-1];
    
    for(int i = 1; i <= n; i++)
        val[i] = INF;
    for(int i = 0; i < n; i++) {
        for(int j = i+1; j <= n; j++) {
            val[j] = min(val[j], val[i] + ((j-i)*(j-i-1))/2 - 2 * (inv[j][j] + inv[i][i] - inv[i][j] - inv[j][i]));
        }
    }
    cout << inv[n][n] + val[n];
}

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