Submission #921413

#	Time	Username	Problem	Language	Result	Execution time	Memory
921413		TAhmed33	Group Photo (JOI21_ho_t3)	C++98	100 / 100	443 ms	174688 KiB

Main

#include <bits/stdc++.h>
using namespace std;
int n, a[5001], dp[5001], pos[5001], inv[5001][5001], calc2[5001][5001];
struct BIT {
	int tree[5001];
	void add (int x) {
		for (; x <= 5000; x += x & (-x)) tree[x]++;
	}
	int get (int x) {
		int sum = 0;
		for (; x > 0; x -= x & (-x)) sum += tree[x];
		return sum;
	}
} cur;
int main () {
	cin >> n;
	for (int i = 1; i <= n; i++) cin >> a[i], pos[a[i]] = i;
	for (int i = 1; i <= n; i++) {
		memset(cur.tree, 0, sizeof(cur.tree));
		for (int j = i; j <= n; j++) {
			inv[i][j] = cur.get(pos[j] - 1) + inv[i][j - 1];
			cur.add(pos[j]);
		}
	}	
	for (int i = 1; i <= n; i++) {
		for (int j = i - 1; j >= 1; j--) {
			if (a[j] > a[i]) {
				calc2[a[i] + 1][a[j]]++;
			}
		}
	}
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= i; j++) {
			calc2[j][i] += calc2[j - 1][i];
		}
	}
	for (int i = 1; i <= n; i++) {
		for (int j = i; j <= n; j++) {
			calc2[i][j] += calc2[i][j - 1];
		}
	}
	for (int i = 1; i <= n; i++) {
		dp[i] = 1e9;
		for (int j = i; j >= 1; j--) {
			int sum = calc2[j][i] - calc2[j][j - 1];
			dp[i] = min(dp[i], dp[j - 1] + sum + inv[j][i]);
		}
	}
	cout << dp[n] << '\n';
}

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