Submission #1081978

#	Time	Username	Problem	Language	Result	Execution time	Memory
1081978		vuavisao	Global Warming (CEOI18_glo)	C++14	100 / 100	437 ms	15216 KiB

glo

#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
using namespace std;

using ll = long long;

const int N = 200'000 + 10;

struct FenWick {
	int n_node = 0;
	vector<int> tree = {};

	void resize(int n) { n_node = n; tree.resize(n + 10, 0); }
	FenWick() {};
	FenWick(int n) { this -> resize(n); };

	void Update(int idx, int val) {
		for( ; idx <= n_node; idx += (idx & - idx)) tree[idx] = max(tree[idx], val);
		return;
	}

	int Query(int idx) {
		int res = 0;
		for( ; idx > 0; idx -= (idx & - idx)) res = max(res, tree[idx]);
		return res;
	}
	
	void reset(int idx) {
		for ( ; idx <= n_node; idx += (idx & - idx)) tree[idx] = 0;
		return;
	}
};

int n, x;
int a[N];

int b[4][N];

int prf[N][2];
int res;

void compress() {
	vector<int> Pos = {};
	for (int i = 1; i <= n; ++ i) {
		Pos.push_back(b[0][i]);
		Pos.push_back(b[1][i]);
		Pos.push_back(b[2][i]);
		Pos.push_back(b[3][i]);
	}
	
	sort(Pos.begin(), Pos.end());
	Pos.resize(unique(Pos.begin(), Pos.end()) - Pos.begin());

	for (int i = 1; i <= n; ++ i) {
		b[0][i] = lower_bound(Pos.begin(), Pos.end(), b[0][i]) - Pos.begin() + 1;
		b[1][i] = lower_bound(Pos.begin(), Pos.end(), b[1][i]) - Pos.begin() + 1;
		b[2][i] = lower_bound(Pos.begin(), Pos.end(), b[2][i]) - Pos.begin() + 1;
		b[3][i] = lower_bound(Pos.begin(), Pos.end(), b[3][i]) - Pos.begin() + 1;
	}
}

void solve() {
	for (int i = 1; i <= n; ++ i) {
		b[0][i] = a[i];
		b[1][i] = a[i] - x;
		b[2][i] = -b[0][i];
		b[3][i] = -b[1][i];
	}
	compress();
	FenWick bit[2];
	for (int i = 0; i < 2; ++ i) {
		bit[i] = FenWick(4 * n);
	}
	for (int i = 1; i <= n; ++ i) {
		int val[2] = {b[0][i], b[1][i]};
		prf[i][0] = bit[0].Query(val[0]);
		bit[0].Update(val[0] + 1, prf[i][0] + 1);

		prf[i][0] = max(prf[i][0], bit[1].Query(val[0]));
		
		prf[i][1] = bit[1].Query(val[1]);
		bit[1].Update(val[1] + 1, prf[i][1] + 1);
	}
	for (int i = 1; i <= n; ++ i) bit[0].reset(b[0][i] + 1);

	for (int i = n; i >= 1; -- i) {
		int best[2] = {bit[0].Query(b[2][i]), bit[0].Query(b[3][i])};
		res = max(res, best[0] + prf[i][0] + 1);
		res = max(res, best[1] + prf[i][1] + 1);
		bit[0].Update(b[2][i] + 1, best[0] + 1);
	}
}

int32_t main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(nullptr); std::cout.tie(nullptr);
	cin >> n >> x;
	for (int i = 1; i <= n; ++ i) cin >> a[i];
	solve();
	reverse(a + 1, a + 1 + n);
	for (int i = 1; i <= n; ++ i) a[i] = -a[i];
	solve();
	cout << res;
	return (0 ^ 0);
}

/// Code by vuavisao

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 13 / 13
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 17 / 17
• Subtask 7: 25 / 25