Submission #343836

#	Time	Username	Problem	Language	Result	Execution time	Memory
343836		emil_physmath	Chessboard (IZhO18_chessboard)	C++17	70 / 100	946 ms	4476 KiB

chessboard

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
using ll = long long;
struct el {
	int a, b, c, d;
};
vector<ll> dv;
vector<el> points;
ll ans;
ll prefans(ll x, ll y, ll k, ll f)
{
	ll ans;
	ll ab = y / k, a;
	a = (ab + 1) / 2;
	a *= k;
	if (ab % 2 == 0)
		a += y % k;
	if (x <= k)
		ans = x * a;
	else
	{
		ll aa = y - a;
		ll q = x / k;
		ans = aa * (q / 2) * k;
		ans += a * ((q + 1) / 2) * k;
		if (q % 2)
			ans += aa * (x % k);
		else ans += a * (x % k);
	}
	if (f == 1)
		return ans;
	else return x * y - ans;
}

long long NumWhite(long long mini, long long minj, long long maxi, long long maxj, long long len)
{
	if (!mini) mini=1;
	if (!minj) minj=1;
	if (mini==1 && minj==1)
	{
        return prefans(maxi, maxj, len, 1);
		long long  ans=0, i=maxi, j=maxj;
		ans+=len*len*(((i/len)*(j/len)+1)/2);
		if ((i/len)%2)
			ans+=(i%len)*((j/len)/2)*len;
		else
			ans+=(i%len)*((j/len+1)/2)*len;
		if ((j/len)%2)
			ans+=(j%len)*((i/len)/2)*len;
		else
			ans+=(j%len)*((i/len+1)/2)*len;
		if ((i/len)%2==(j/len)%2)
			ans+=(i%len)*(j%len);
		return ans;
	}
	return NumWhite(1, 1, maxi, maxj, len)-
		NumWhite(1, 1, maxi, minj-1, len)-NumWhite(1, 1, mini-1, maxj, len)+
		NumWhite(1, 1, mini-1, minj-1, len);
}

int main()
{
	ll n, k;
	cin >> n >> k;
	ans = n * n;
	for (int i = 1; i < n; i++)
		if (n % i == 0)dv.push_back(i);
	for (int i = 0; i < k; i++)
	{
		int a, b, c, d;
		cin >> a >> b >> c >> d;
		points.push_back({ a,b,c,d });
	}/*
	for (auto p : points)
		cerr << p.first << ' ' << p.second << '\n';*/
	for (ll d : dv)
	{
		ll blackans;
		ll q = n / d;
		if (q % 2)
			blackans = (n * n - d * d) / 2 + d * d;
		else blackans = n * n / 2;
		ll whiteans = n * n - blackans;
        blackans = n * n - NumWhite(1, 1, n, n, d);
        whiteans = NumWhite(1, 1, n, n, d);
		//cerr << blackans << ' ' << whiteans << " 1, 1, " << n << ", " << n << " " << NumWhite(1, 1, n, n, d) << '\n';
		for (auto p : points)
		{
            blackans -= (p.d - p.b + 1) * (p.c - p.a + 1) - NumWhite(p.a, p.b, p.c, p.d, d);
            whiteans -= NumWhite(p.a, p.b, p.c, p.d, d);
            whiteans += (p.d - p.b + 1) * (p.c - p.a + 1) - NumWhite(p.a, p.b, p.c, p.d, d);
            blackans += NumWhite(p.a, p.b, p.c, p.d, d);
			//blackans += prefans(p.c, p.d, d, 1) - prefans(p.a - 1, p.d, d, 1) - prefans(p.c, p.b - 1, d, 1) + 2 * prefans(p.a - 1, p.b - 1, d, 1);
			//whiteans += prefans(p.c, p.d, d, 0) - prefans(p.a - 1, p.d, d, 0) - prefans(p.c, p.b - 1, d, 0) + 2 * prefans(p.a - 1, p.b - 1, d, 0);
		}
		//cerr << blackans << ' ' << whiteans << '\n';
		ans = min(ans, min(blackans, whiteans));
	}
	cout << ans;
	return 0;
}

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