Submission #415481

#	Time	Username	Problem	Language	Result	Execution time	Memory
415481		amoo_safar	Group Photo (JOI21_ho_t3)	C++17	100 / 100	268 ms	67512 KiB

Main

// vaziat meshki-ghermeze !
#include <bits/stdc++.h>

#define pb push_back
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define debug(x) cerr << #x << " : " << x << '\n'

using namespace std;

typedef long long ll;
typedef long double ld;
typedef string str;
typedef pair<ll, ll> pll;

const ll Mod = 1000000007LL;
const int N = 5e3 + 10;
const ll Inf = 2242545357980376863LL;
const ll Log = 30;

int p[N], rv[N];
int sm[N][N];
int dp[N];

int C2(int x){ return x * (x - 1) / 2; }

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 >> p[i];
		rv[p[i]] = i;
	}
	for(int i = 1; i <= n; i++){
		for(int j = i + 1; j <= n; j++){
			if(rv[i] > rv[j])
				sm[i][j] ++;
		}
	}
	for(int i = 1; i <= n; i++)
		for(int j = i - 1; j >= 1; j--)
			sm[j][i] += sm[j + 1][i] + sm[j][i - 1] - sm[j + 1][i - 1];
	
	memset(dp, 31, sizeof dp);
	dp[0] = 0;
	for(int i = 0; i < n; i++){
		for(int j = i + 1; j <= n; j++)
			dp[j] = min(dp[j], dp[i] - sm[i + 1][j] + C2(j - i) - sm[i + 1][j]);
	}
	cout << dp[n] + sm[1][n] << '\n';
	return 0;
}

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