Submission #343838

#	Time	Username	Problem	Language	Result	Execution time	Memory
343838		emil_physmath	Chessboard (IZhO18_chessboard)	C++17	100 / 100	889 ms	6024 KiB

chessboard

#include <iostream>
#include <stdio.h>
using namespace std;
const int MAXK=100005;

long long mini[MAXK], maxi[MAXK], minj[MAXK], maxj[MAXK];

long long NumWhite(long long, long long, long long, long long, long long cellLen);
long long FindAns(long long n, long long k, long long cellLen);
int main()
{
	long long n, k;
	cin>>n>>k;
	for (int i=0; i<k; i++)
		scanf("%lld%lld%lld%lld", mini+i, minj+i, maxi+i, maxj+i);
	long long  ans=n*n;
	for (int cellLen=1; cellLen*cellLen<=n; cellLen++)
		if (n%cellLen==0)
		{
			ans=min(ans, FindAns(n, k, cellLen));
			ans=min(ans, FindAns(n, k, n/cellLen));
		}
	cout<<ans<<'\n';

	char I;
	cin >> I;
	return 0;
}

long long FindAns(long long n, long long k, long long cellLen)
{
	if (cellLen>=n) return n*n;
	long long shouldWhite=0, shouldBlack=0, isBlack=0;
	for (int i=0; i<k; i++)
	{
		shouldWhite+=NumWhite(mini[i], minj[i], maxi[i], maxj[i], cellLen);
		isBlack+=(maxi[i]-mini[i]+1)*(maxj[i]-minj[i]+1);
	}
	shouldBlack=(n*n-NumWhite(1, 1, n, n, cellLen))-(isBlack-shouldWhite);
	return min(shouldWhite+shouldBlack, n*n-(shouldWhite+shouldBlack));
}
using ll = long long;
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);
}

Compilation message (stderr)

chessboard.cpp: In function 'int main()':
chessboard.cpp:15:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   15 |   scanf("%lld%lld%lld%lld", mini+i, minj+i, maxi+i, maxj+i);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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