Submission #784646

#	Time	Username	Problem	Language	Result	Execution time	Memory
784646		ToniB	Chessboard (IZhO18_chessboard)	C++17	47 / 100	2096 ms	6860 KiB

chessboard

#include <bits/stdc++.h>
#define X first
#define Y second
using namespace std;
const int MAXN = 1e5 + 5;
const int OFF = 1 << 18;
typedef long long ll;

int n, k, tour[OFF];
vector<pair<int, int> > v[MAXN];
bool prop[OFF];

void propagate(int& x, int& l, int& r){
	prop[x] = 0;
	tour[x] = r - l + 1 - tour[x];
	if(l != r){
		prop[x * 2 + 1] ^= 1;
		prop[x * 2 + 2] ^= 1;
	}
}

void upd(int x, int l, int r, int ql, int qr){
	if(prop[x]) propagate(x, l, r);
	if(ql <= l && r <= qr){
		prop[x] = 1;
		propagate(x, l, r);
		return ;
	}
	if(ql > r || l > qr) return ;
	int mid = (l + r) >> 1;
	upd(x * 2 + 1, l, mid, ql, qr);
	upd(x * 2 + 2, mid + 1, r, ql, qr);
	tour[x] = tour[x * 2 + 1] + tour[x * 2 + 2];
}

inline ll solve(int& k){
	ll ret = 5e9;
	for(int b = 0; b < 2; ++b){
		memset(tour, 0, sizeof tour);
		memset(prop, 0, sizeof prop);
		ll cur = 0;
		for(int i = b * k; i < n; i += 2 * k){
			upd(0, 0, n - 1, i, i + k - 1);
		}
		for(int i = 0; i < n; ++i){
			for(pair<int, int>& p : v[i]){
				upd(0, 0, n - 1, p.X, p.Y);
			}
			if(i % k == 0) upd(0, 0, n - 1, 0, n - 1);
			cur += tour[0];
		}
		ret = min(ret, cur);
	}
	return ret;
}

int main(){
	ios_base::sync_with_stdio(false); cin.tie(0);

	cin >> n >> k;
	for(int i = 0; i < k; ++i){
		int x1, y1, x2, y2;
		cin >> x1 >> y1 >> x2 >> y2;
		--x1, --y1, --x2, --y2;
		v[x1].push_back({y1, y2});
		v[x2 + 1].push_back({y1, y2});
	}
	ll ans = 5e9;
	for(int i = 1; i < n; ++i){
		if(n % i == 0){
			ans = min(ans, solve(i));
		}
	}
	cout << ans;
	return 0;
}

• Subtask 1: 8 / 8
• Subtask 2: 8 / 8
• Subtask 3: 15 / 15
• Subtask 4: 16 / 16
• Subtask 5: 0 / 23
• Subtask 6: 0 / 30