Submission #823542

#	Time	Username	Problem	Language	Result	Execution time	Memory
823542		phoenix	Rectangles (IOI19_rect)	C++17	100 / 100	2049 ms	625124 KiB

rect

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

using namespace std;
using ll = long long;


struct FenwickTree {
    vector<int> bit;  // binary indexed tree
    int n;
    FenwickTree(int n) {
        this->n = n;
        bit.assign(n, 0);
    }
    FenwickTree(vector<int> const &a) : FenwickTree(a.size()) {
        for (size_t i = 0; i < a.size(); i++)
            add(i, a[i]);
    }
    int sum(int r) {
        int ret = 0;
        for (; r >= 0; r = (r & (r + 1)) - 1)
            ret += bit[r];
        return ret;
    }
    int sum(int l, int r) {
        return sum(r) - sum(l - 1);
    }
    void add(int idx, int delta) {
        for (; idx < n; idx = idx | (idx + 1))
            bit[idx] += delta;
    }
};

// O(nlogn)
vector<pair<int, int>> get_segments(vector<int> a) {
	int n = (int)a.size();
	
	vector<pair<int, int>> res;
	vector<int> st;
	for(int i = 0; i < n; i++) {
		while(!st.empty() && a[st.back()] < a[i]) {
			if(i - st.back() > 1) res.push_back({st.back() + 1, i - 1});
			st.pop_back();
		} 
		if(!st.empty()) {
			if(i - st.back() > 1) res.push_back({st.back() + 1, i - 1});
			if(a[st.back()] == a[i]) st.pop_back();
		}
		st.push_back(i);
	}
	return res;	
}

const int N = 2505;

struct segment {
	int l, d;
};

vector<segment> h[N][N], g[N][N];

ll count_rectangles(vector<vector<int>> a) {
	int n = (int)a.size(), m = (int)a[0].size();
	if(n < 3 || m < 3) return 0;
	for(int i = 0; i < n; i++) {
		vector<pair<int, int>> s = get_segments(a[i]);
		for(auto [l, r] : s) 
			g[i][r].push_back({l, 0});
	}
	for(int i = 0; i < m; i++) {
		vector<int> b;
		for(int j = 0; j < n; j++) 
			b.push_back(a[j][i]);
		vector<pair<int, int>> s = get_segments(b);
		for(auto [l, r] : s) 
			h[r][i].push_back({l, 0});
	}
	for(int i = 0; i < n; i++) {
		int cnt[n] = {};
		bool us[n] = {};
		for(int j = 0; j < m; j++) {
			if(!j) {
				for(auto c : h[i][j]) 
					cnt[c.l]++;
			} else {
				for(auto c : h[i][j])
					us[c.l] = 1;
				for(auto c : h[i][j - 1])
					if(!us[c.l]) cnt[c.l] = 0;
				
				for(auto c : h[i][j]) {
					cnt[c.l]++;
					us[c.l] = 0;
				}
			}
			for(auto &c : h[i][j]) {
				c.d = cnt[c.l];
			}
		}
	}
	for(int i = 0; i < m; i++) {
		int cnt[m] = {};
		bool us[m] = {};
		for(int j = 0; j < n; j++) {
			if(!j) {
				for(auto c : g[j][i]) 
					cnt[c.l]++;
			} else {
				for(auto c : g[j][i]) 
					us[c.l] = 1;
				for(auto c : g[j - 1][i]) 
					if(!us[c.l]) 
						cnt[c.l] = 0;
				for(auto c : g[j][i]) {
					cnt[c.l]++;
					us[c.l] = 0;
				}
			}
			for(auto &c : g[j][i])
				c.d = cnt[c.l];
		}
	}
	ll ans = 0;
	FenwickTree st(n);
	for(int i = 0; i < n; i++) {
		for(int j = 0; j < m; j++) {
			sort(g[i][j].begin(), g[i][j].end(), [](segment x, segment y) {return x.l < y.l;});
			sort(h[i][j].begin(), h[i][j].end(), [](segment x, segment y) {return x.d > y.d;});
			int h_l = 0;
			for(segment cur : g[i][j]) {
				while(h_l < (int)h[i][j].size() && j - h[i][j][h_l].d < cur.l) {
					st.add(h[i][j][h_l++].l, +1);
				} 
				ans += st.sum(i - cur.d + 1, i);
			}
			while(h_l > 0) 
				st.add(h[i][j][--h_l].l, -1);
		}
	}
	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: 28 / 28