Submission #1227057

#	Time	Username	Problem	Language	Result	Execution time	Memory
1227057		chaeryeong	Chorus (JOI23_chorus)	C++20	61 / 100	828 ms	98480 KiB

chorus

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int inf = 1e9;
int n, k, dp[5002][5002], t[5002], P[5002];
vector <int> ii[2];
string s;
int choose (int x) {
	return x * (x - 1) / 2;
}
void recurse (int l1, int r1, int l2, int r2, int j) {
	if (l1 > r1) {
		return;
	}
	int i = (l1 + r1) / 2;
	dp[i][j] = inf;
	int opt = -1;
	for (int p = min(r2, t[i]); p >= l2; p--) {
		if (dp[i][j] > dp[p - 1][j - 1] + ii[0][i] * (t[i] - p) - choose(t[i] - p) - (P[t[i] - 1] - P[p - 1])) {
			dp[i][j] = dp[p - 1][j - 1] + ii[0][i] * (t[i] - p) - choose(t[i] - p) - (P[t[i] - 1] - P[p - 1]);
			opt = p;
		}
	}
	recurse(l1, i - 1, l2, opt, j);
	recurse(i + 1, r1, opt, r2, j);
}
void solve () {
	cin >> n >> k >> s;
	int bad = 0;
	int cur = 0;
	for (int i = 0; i < 2 * n; i++) {
		if (s[i] == 'B') {
			cur--;
		} else {
			cur++;
		}
		if (cur < 0) {
			int j = i;
			while (s[j] != 'A') {
				j++;
			}
			bad += j - i;
			swap(s[i], s[j]);
			i--; cur++;
		}
	}
	ii[0].push_back(0);
	ii[1].push_back(0);
	for (int i = 0; i < 2 * n; i++) {
		ii[s[i] - 'A'].push_back(i + 1);
	}
	for (int i = 1; i <= n; i++) {
		P[i] = P[i - 1] + ii[1][i];
	}
	for (int i = 1; i <= n; i++) {
		dp[i][0] = inf;
	}
	for (int j = 1; j <= k; j++) {
		int l = 1;
		for (int i = 1; i <= n; i++) {
			dp[i][j] = inf;
			while (ii[1][l] < ii[0][i]) {
				l++;
			}
			t[i] = l;
		}
		recurse(1, n, 1, n, j);
	}
	cout << bad + dp[n][k] << '\n';
}	
signed main () {
	ios::sync_with_stdio(0); cin.tie(0);
	int tc = 1; //cin >> tc;
	while (tc--) solve();
}

• Subtask 1: 16 / 16
• Subtask 2: 24 / 24
• Subtask 3: 21 / 21
• Subtask 4: 0 / 26
• Subtask 5: 0 / 13