Submission #979000

#	Time	Username	Problem	Language	Result	Execution time	Memory
979000		penguin133	Group Photo (JOI21_ho_t3)	C++17	100 / 100	338 ms	313732 KiB

Main

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

#define int long long
#define pi pair<int, int>
#define pii pair<int, pi>
#define fi first
#define se second
#ifdef _WIN32
#define getchar_unlocked _getchar_nolock
#endif
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

int dp[5005], A[5005], pos[5005], P[5005][5005], col[5005][5005], n;

void solve(){
	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])P[i][j]++;
			P[i][j] += P[i][j - 1];
		}
	}
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= n; j++){
			col[i][j] = col[i - 1][j] + P[i][j];
		}
	}
	dp[0] = 0;
	for(int i = 1; i <= n; i++){
		dp[i] = 1e18;
		for(int j = i; j >= 1; j--){
			//arrange j..i in i..j
			int cnt = 0;
			/*
			for(int k = 1; k < j; k++){
				int tmp = P[k][i] - P[k][j - 1];
				cnt += (i - j + 1) - tmp;
			}
			*/
			cnt += (i - j + 1) * (j - 1) - col[j - 1][i] + col[j - 1][j - 1];
			/*
			for(int k = j; k <= i; k++){
				int tmp = P[k][i] - P[k][k];
				//cnt += i - k - tmp;
				cnt += tmp;
			}
			*/
			cnt += col[i][i] - col[j - 1][i];
			dp[i] = min(dp[i], cnt + dp[j - 1]);
		}
		//cout << dp[i] << ' ';
	}
	cout << dp[n];
	//cout << *min_element(dp[n] + 1, dp[n] + n + 1);
}

main(){
	ios::sync_with_stdio(0);cin.tie(0);
	int tc = 1;
	//cin >> tc;
	for(int tc1=1;tc1<=tc;tc1++){
		// cout << "Case #" << tc1 << ": ";
		solve();
	}
}

Compilation message (stderr)

Main.cpp:62:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   62 | main(){
      | ^~~~

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