Submission #802341

#	Time	Username	Problem	Language	Result	Execution time	Memory
802341		Sohsoh84	Giraffes (JOI22_giraffes)	C++17	59 / 100	3147 ms	91472 KiB

giraffes

// Wounds should become scars but I'm cracked instead U+1FAE0
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> pll;

#define all(x)			(x).begin(),(x).end()
#define X			first
#define Y			second
#define sep			' '
#define endl			'\n'
#define debug(x)		cerr << #x << ": " <<  x << endl;

const ll MAXN = 500 + 10;
const ll TMAX = 1e6 + 10;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int dp[MAXN][MAXN][MAXN], n, P[TMAX], ind[TMAX];

inline int rand_perm() {
	int l = 1, r = n;
	int fl = 1, fr = n;
	int ans = n;

	for (int i = 1; i <= n; i++) {
		if (P[l] == fl) {
			ans--;
			l++;
			fl++;
		} else if (P[l] == fr) {
			ans--;
			l++;
			fr--;
		} else if (P[r] == fl) {
			ans--;
			r--;
			fl++;
		} else if (P[r] == fr) {
			ans--;
			r--;
			fr--;
		} else {
			int tfl = fl;
			int tfr = fr;

			if (ind[fl] < l || ind[fl] > r) tfl++;
			else if (ind[fr] < l || ind[fr] > r) tfr--;
			else if (rng() % 2) tfl++;
			else tfr--;

			if (P[l] < fl || P[l] > fr) l++;
			else if (P[r] < fl || P[r] > fr) r--;
			else if (rng() % 2) l++;
			else r--;

			fl = tfl;
			fr = tfr;
		}
	}

	return ans;
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> P[i];
		ind[P[i]] = i;
	}

	if (n < MAXN) {
		for (int len = 1; len <= n; len++) {
			for (int l = 1; l <= n - len + 1; l++) {
				for (int tl = 1; tl <= n - len + 1; tl++) {
					int r = l + len - 1;
					int tr = tl + len - 1;

					if (P[l] == tl) dp[len][l][tl] = dp[len - 1][l + 1][tl + 1] + 1;
					else if (P[r] == tl) dp[len][l][tl] = dp[len - 1][l][tl + 1] + 1;
					else if (P[l] == tr) dp[len][l][tl] = dp[len - 1][l + 1][tl] + 1;
					else if (P[r] == tr) dp[len][l][tl] = dp[len - 1][l][tl] + 1;
					else dp[len][l][tl] = max({
							dp[len - 1][l][tl], 
							dp[len - 1][l + 1][tl], 
							dp[len - 1][l][tl + 1], 
							dp[len - 1][l + 1][tl + 1]
							});
				}
			}
		}

		cout << n - dp[n][1][1] << endl;
	} else {
		int fuck = 10000000 * 13 / n;

		int ans = n;
		while (fuck--) {
			ans = min(ans, rand_perm());
		}

		cout << ans << endl;
	}

	return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 22 / 22
• Subtask 3: 27 / 27
• Subtask 4: 0 / 41