Submission #760331

#	Time	Username	Problem	Language	Result	Execution time	Memory
760331		8e7	Sequence (APIO23_sequence)	C++17	70 / 100	2086 ms	56272 KiB

sequence

#include "sequence.h"
//Challenge: Accepted
#include <bits/stdc++.h>
using namespace std;
#ifdef zisk
void debug(){cout << endl;}
template<class T, class ... U> void debug(T a, U ...b){cout << a << " ", debug(b...);}
template<class T> void pary(T l, T r) {
	while (l != r) cout << *l << " ", l++;
	cout << endl;
}
#else
#define debug(...) 0
#define pary(...) 0
#endif
#define ll long long
#define maxn 500005
#define ff first
#define ss second
#define pii pair<int, int>
const int inf = 1<<30;
struct segtree{
	int ma[4*maxn], mi[4*maxn], tag[4*maxn], tag2[4*maxn];
	void init(int cur, int l, int r) {
		if (r <= l) return;
		tag[cur] = 0;
		if (r - l == 1) {
			ma[cur] = mi[cur] = l+1;
			return;
		}
		int m = (l + r) / 2;
		init(cur*2, l, m), init(cur*2+1, m, r);
		ma[cur] = max(ma[cur*2], ma[cur*2+1]);
		mi[cur] = min(mi[cur*2], mi[cur*2+1]);
	}
	void push(int cur, int l, int r) {
		ma[cur] += tag[cur];
		mi[cur] += tag[cur];
		if (r - l > 1) {
			tag[cur*2] += tag[cur];
			tag[cur*2+1] += tag[cur];
		}
		tag[cur] = 0;
	}
	void modify(int cur, int l, int r, int ql, int qr, int v) {
		if (r <= l || ql >= r || qr <= l) return;
		push(cur, l, r);
		if (ql <= l && qr >= r) {
			tag[cur] += v;
			return;
		}
		int m = (l + r) / 2;
		modify(cur*2, l, m, ql, qr, v);
		modify(cur*2+1, m, r, ql, qr, v);
		push(cur*2, l, m), push(cur*2+1, m, r);
		ma[cur] = max(ma[cur*2], ma[cur*2+1]);
		mi[cur] = min(mi[cur*2], mi[cur*2+1]);
	}
	pii query(int cur, int l, int r, int ql, int qr) { //(ma, mi)
		if (r <= l || ql >= r || qr <= l) return {-inf, inf};
		push(cur, l, r);
		if (ql <= l && qr >= r) return make_pair(ma[cur], mi[cur]);
		int m = (l + r) / 2;
		pii pl = query(cur*2, l, m, ql, qr), pr = query(cur*2+1, m, r, ql, qr);	
		pl.ff = max(pl.ff, pr.ff);
		pl.ss = min(pl.ss, pr.ss);
		return pl;
	}
	int get(int cur, int l, int r, int x) { 
		if (r <= l) return 0;
		push(cur, l, r);
		if (r - l == 1) return ma[cur];
		int m = (l + r) / 2;
		if (x < m) return get(cur*2, l, m, x);
		else return get(cur*2+1, m, r, x);
	}
} pref, pref2;
vector<int> pos[maxn];
int sequence(int N, std::vector<int> A) {
	pref.init(1, 0, N);
	pref2.init(1, 0, N);
	for (int i = 0;i < N;i++) {
		pos[A[i]].push_back(i);
	}

	//for (int j = 0;j < N;j++) cout << pref.get(1,0, N, j) << " ";
	//cout << endl;
	
	
	int ans = 1;
	
	for (int i = 1;i <= N;i++) {
		int siz = pos[i].size();
		if (siz == 0) continue;
		for (int j = 0;j < siz;j++) {
			pref.modify(1, 0, N, pos[i][j], N, -2);
		}
		//for (int j = 0;j < N;j++) cout << pref.get(1,0, N, j) << " ";
		//cout << endl;
		auto check = [&] (int ind, int j) {
			int l = pos[i][ind], r = pos[i][j], cnt = j - ind + 1; //[l, r]
			pii pl = pref.query(1, 0, N, 0, l), pr = pref.query(1, 0, N, r, N);
			pl.ff = max(pl.ff, 0), pl.ss = min(pl.ss, 0);
			pii p = {pr.ff - pl.ss, pr.ss - pl.ff};

			pl = pref2.query(1, 0, N, 0, l), pr = pref2.query(1, 0, N, r, N);
			pl.ff = max(pl.ff, 0), pl.ss = min(pl.ss, 0);
			pii p2 = {pr.ff - pl.ss, pr.ss - pl.ff};
			//debug(l, r, p.ss, p2.ff);	
			//debug(ind, j, p.ss, p.ff);
			if ((p.ss <= 0  && 0 <= p2.ff)) {
				ans = max(ans, j - ind + 1);
				return true;
			} else {
				return false;
			}
		};
		
		int low = ans, up = siz+1;	
		while (low < up - 1) {
			int mid = (low + up) / 2;
			int poss = 0;
			for (int x = 0;x <= siz - mid;x++) {
				if (check(x, x + mid - 1)) {
					poss = 1;
					break;
				}
			}
			if (poss) low = mid;
			else up = mid;
		}
		
		for (int j = 0;j < siz;j++) {
			pref2.modify(1, 0, N, pos[i][j], N, -2);
		}

	}
 	return ans;
}

Compilation message (stderr)

sequence.cpp: In lambda function:
sequence.cpp:101:40: warning: unused variable 'cnt' [-Wunused-variable]
  101 |    int l = pos[i][ind], r = pos[i][j], cnt = j - ind + 1; //[l, r]
      |                                        ^~~

• Subtask 1: 11 / 11
• Subtask 2: 17 / 17
• Subtask 3: 7 / 7
• Subtask 4: 0 / 12
• Subtask 5: 13 / 13
• Subtask 6: 22 / 22
• Subtask 7: 0 / 18