Submission #823807

#	Time	Username	Problem	Language	Result	Execution time	Memory
823807		dxz05	Rectangles (IOI19_rect)	C++17	72 / 100	5066 ms	734624 KiB

rect

#pragma GCC optimize("Ofast,O3,unroll-loops")
#pragma GCC target("avx,avx2")

#include "rect.h"
#include <bits/stdc++.h>

using namespace std;

vector<pair<int, int>> find_borders(const vector<int> &a){
	int n = (int) a.size();

	stack<int> st;
	vector<int> l(n), r(n);
	for (int i = 0; i < n; i++){
		while (!st.empty() && a[st.top()] < a[i]) st.pop();
		l[i] = (st.empty() ? -1 : st.top());
		st.push(i);
	}

	while (!st.empty()) st.pop();

	for (int i = n - 1; i >= 0; i--){
		while (!st.empty() && a[st.top()] < a[i]) st.pop();
		r[i] = (st.empty() ? n : st.top());
		st.push(i);
	}

	vector<pair<int, int>> ans;
	set<pair<int, int>> s1; // (i, r[i])
	set<pair<int, int>> s2; // (r[i], i)
	for (int j = 0; j < n; j++){
		while (!s2.empty()){
			int i = s2.begin()->second;
			if (r[i] < j){
				s1.erase(make_pair(i, r[i]));
				s2.erase(make_pair(r[i], i));
			} else {
				break;
			}
		}

		assert(s1.size() == s2.size());

		auto it = s1.end();
		while (true){
			if (it == s1.begin()) break;
			it--;

			int i = it->first;
			if (i < l[j]) break;

			if (i + 1 < j) ans.emplace_back(i + 1, j - 1);
		}

		s1.emplace(j, r[j]);
		s2.emplace(r[j], j);
	}

	return ans;
}

const int MaxN = 2500;

vector<pair<int, int>> per_col[MaxN][MaxN];
vector<pair<int, int>> per_row[MaxN][MaxN];

vector<tuple<int, int, int>> opening[MaxN];
set<pair<int, int>> vals_to_add[MaxN];

long long count_rectangles(vector<vector<int>> A) {
	int n = (int) A.size(), m = (int) A[0].size();

	for (int i = 1; i + 1 < n; i++){
		vector<pair<int, int>> f = find_borders(A[i]);

		for (auto [l, r] : f){
			auto &v = per_col[l][r];
			if (v.empty() || v.back().second != i - 1){
				v.emplace_back(i, i);
			} else {
				v.back().second++;
			}
		}
	}

	for (int j = 1; j + 1 < m; j++){
		vector<int> col(n);
		for (int i = 0; i < n; i++) col[i] = A[i][j];
		vector<pair<int, int>> f = find_borders(col);
		for (auto [x, y] : f){
			auto &v = per_row[x][y];
			if (v.empty() || v.back().second != j - 1){
				v.emplace_back(j, j);
			} else {
				v.back().second++;
			}
		}
	}

	for (int x = 0; x < n; x++){
		for (int y = x; y < n; y++){
			for (auto [l, r] : per_row[x][y]){
				opening[l].emplace_back(r, x, y);
			}
		}
	}

	long long ans = 0;
	for (int l = 1; l < m - 1; l++){
		for (auto [r, x, y] : opening[l]){
			vals_to_add[r].emplace(x, y);
		}

		vector<pair<int, int>> vals;
 		for (int r = m - 2; r >= l; r--){
			auto &v = per_col[l][r];

			vector<pair<int, int>> _vals;
			merge(vals.begin(), vals.end(), vals_to_add[r].begin(), vals_to_add[r].end(), std::back_inserter(_vals));
			vals.swap(_vals);

			int sz = (int) vals.size();
			int i = 0;

			for (auto [X, Y] : v){
				while (i < sz && vals[i].first <= Y){
					int x = vals[i].first, y = vals[i].second;
					if (X <= x && y <= Y){
						ans++;
					}
					i++;
				}
			}

		}
	}

	return ans;
}

• Subtask 1: 8 / 8
• Subtask 2: 7 / 7
• Subtask 3: 12 / 12
• Subtask 4: 22 / 22
• Subtask 5: 10 / 10
• Subtask 6: 13 / 13
• Subtask 7: 0 / 28