Submission #874664

#	Time	Username	Problem	Language	Result	Execution time	Memory
874664		Itamar	Sequence (APIO23_sequence)	C++17	100 / 100	1242 ms	97436 KiB

sequence

#include "sequence.h"

#include <vector>
using namespace std;
#define vi vector<int>
const int siz = 5e5 + 1;
vi his[siz];
#define pi pair<int,int>
#define x first
#define y second
struct node {
	int l, r, mid, minl, minr, maxl, maxr,sum1,sum2;
	node* sl, * sr;
	node(int li, int ri) {
		l = li, r = ri, mid = (l + r) / 2, minl = -(r - l + 1), minr = -(r - l + 1), maxl = 0, maxr = 0,sum1=minr,sum2=minr;
		if (l < r) {
			sl = new node(l, mid);
			sr = new node(mid + 1, r);
		}
	}
	void update(int i, int p) {
		if (l == r) {
			
			if (p == 2) {
				sum1 = 1, minl = 0, minr = 0;
			}
			else {
				sum2 = 1, maxl = 1, maxr = 1;
			}
		}
		else {
			if (i <= mid)sl->update(i, p);
			else sr->update(i, p);
			if (p == 2) {
				sum1 = sl->sum1 + sr->sum1;
				minl = min(sl->minl, sl->sum1 + sr->minl);
				minr = min(sr->minr, sr->sum1 + sl->minr);
			}
			else {
				sum2 = sl->sum2 + sr->sum2;

				maxl = max(sl->maxl, sl->sum2 + sr->maxl);
				maxr = max(sr->maxr, sr->sum2 + sl->maxr);
			}
		}
	}
	int query1(int a, int b) {
		 if (a <= l && b >= r)return sum1;
		 if (b <= mid)return min(sl->query1(a, b), sl->query1(a, mid) + sr->minl);
		 if (a > mid)return min(sr->query1(a, b), sr->query1(mid + 1, b) + sl->minr);
		 return sl->query1(a, mid) + sr->query1(mid+1, b);
	}
	int query2(int a, int b) {
		if (a <= l && b >= r)return sum2;
		if (b <= mid)return max(sl->query2(a, b), sl->query2(a, mid) + sr->maxl);
		if (a > mid)return max(sr->query2(a, b), sr->query2(mid + 1, b) + sl->maxr);
		return sl->query2(a, mid) + sr->query2(mid+1, b);
	}
};

int sequence(int N, std::vector<int> A) {
	for (int i = 0; i < N; i++)his[A[i]].push_back(i);
	int ans = 1;
	node* seg = new node(0, N-1);
	for (int i = 0; i <= N; i++) {
		if (his[i].empty())continue;
		
		int it1 = 0, it2 = 0;
		for (int a : his[i])seg->update(a, 1);

		while (it2+1 < his[i].size()) {
			if (his[i].size() - it1 <= ans)break;
			pi p = { seg->query1(his[i][it1], his[i][it2 + 1]),seg->query2(his[i][it1],his[i][it2 + 1]) };
			
			if (p.x> 0 || p.y< 0) {
				it1++;
			}
			else {
				it2++;
			}
			if (it1 > it2)it2++;
			ans = max(ans, it2 - it1 + 1);
		}

		for (int a : his[i])seg->update(a, 2);
	}

	return ans;
}

Compilation message (stderr)

sequence.cpp: In function 'int sequence(int, std::vector<int>)':
sequence.cpp:71:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |   while (it2+1 < his[i].size()) {
      |          ~~~~~~^~~~~~~~~~~~~~~
sequence.cpp:72:28: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   72 |    if (his[i].size() - it1 <= ans)break;
      |        ~~~~~~~~~~~~~~~~~~~~^~~~~~

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