Submission #625553

#	Time	Username	Problem	Language	Result	Execution time	Memory
625553		timmyfeng	Radio Towers (IOI22_towers)	C++17	100 / 100	2384 ms	101648 KiB

towers

#include "towers.h"

#include <bits/stdc++.h>
using namespace std;

#include <bits/extc++.h>
using namespace __gnu_pbds;

template <class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

vector<ordered_set<pair<int, int>>> settree;
vector<int> min_h, max_h, up, down, h;
int n;

void build(int u, int l, int r) {
	if (l + 1 == r) {
		min_h[u] = max_h[u] = h[l];
	} else {
		int m = (l + r) / 2;

		build(2 * u, l, m);
		build(2 * u + 1, m, r);

		min_h[u] = min(min_h[2 * u], min_h[2 * u + 1]);
		max_h[u] = max(max_h[2 * u], max_h[2 * u + 1]);
		up[u] = max({up[2 * u], up[2 * u + 1], max_h[2 * u + 1] - min_h[2 * u]});
		down[u] = max({down[2 * u], down[2 * u + 1], max_h[2 * u] - min_h[2 * u + 1]});
	}
}

void update(int a, int x, int u = 1, int l = 0, int r = n) {
	if (l + 1 < r) {
		int m = (l + r) / 2;
		if (a < m) update(a, x, 2 * u, l, m);
		else update(a, x, 2 * u + 1, m, r);
	}
	settree[u].insert({x, a});
}

void init(int n, vector<int> h) {
	::h = h, ::n = n;

	vector<pair<int, int>> points;
	for (int i = 0; i < n; ++i) {
		points.push_back({h[i], i});
	}

	sort(points.begin(), points.end());

	settree.resize(4 * n);

	set<array<int, 3>> ranges = {{INT_MIN, INT_MIN, -1}, {INT_MAX, INT_MAX, -1}};
	for (auto [hi, i] : points) {
		auto nxt = ranges.upper_bound({i, i, hi});
		auto prv = nxt; --prv;

		if (nxt->at(0) == i + 1 && prv->at(1) == i - 1) {
			update(i, hi - max(nxt->at(2), prv->at(2)));
		}

		int l = i, r = i, x = hi;
		if (nxt->at(0) == i + 1) {
			r = nxt->at(1);
			x = min(x, nxt->at(2));
			ranges.erase(nxt);
		}
		if (prv->at(1) == i - 1) {
			l = prv->at(0);
			x = min(x, prv->at(2));
			ranges.erase(prv);
		}
		
		ranges.insert({l, r, x});
	}

	max_h.resize(4 * n);
	min_h.resize(4 * n);
	up.resize(4 * n);
	down.resize(4 * n);

	build(1, 0, n);
}

int find_first(int a, int d, int &prefix, int u = 1, int l = 0, int r = n) {
	if (r <= a) return n;
	if (l + 1 == r) {
		if (h[l] - prefix >= d) return l;
		prefix = min(prefix, min_h[u]);
		return n;
	}

	if (l >= a && up[u] < d && max_h[u] - prefix < d) {
		prefix = min(prefix, min_h[u]);
		return n;
	}

	int m = (l + r) / 2;
	int b = find_first(a, d, prefix, 2 * u, l, m);
	return b == n ? find_first(a, d, prefix, 2 * u + 1, m, r) : b;
}

int find_last(int b, int d, int &suffix, int u = 1, int l = 0, int r = n) {
	if (l > b) return -1;
	if (l + 1 == r) {
		if (h[l] - suffix >= d) return l;
		suffix = min(suffix, min_h[u]);
		return -1;
	}

	if (r <= b + 1 && down[u] < d && max_h[u] - suffix < d) {
		suffix = min(suffix, min_h[u]);
		return -1;
	}

	int m = (l + r) / 2;
	int a = find_last(b, d, suffix, 2 * u + 1, m, r);
	return a == -1 ? find_last(b, d, suffix, 2 * u, l, m) : a;
}

int query(int a, int b, int d, int u = 1, int l = 0, int r = n) {
	if (a >= b || b <= l || r <= a) return 0;
	if (a <= l && r <= b) return settree[u].size() - settree[u].order_of_key({d, -1});
	int m = (l + r) / 2;
	return query(a, b, d, 2 * u, l, m) + query(a, b, d, 2 * u + 1, m, r);
}

int max_towers(int l, int r, int d) {
	int temp = h[l];
	l = find_first(l, d, temp);
	temp = h[r];
	r = find_last(r, d, temp);

	return 1 + query(l, r + 1, d);
}

• Subtask 1: 4 / 4
• Subtask 2: 11 / 11
• Subtask 3: 12 / 12
• Subtask 4: 14 / 14
• Subtask 5: 17 / 17
• Subtask 6: 19 / 19
• Subtask 7: 23 / 23