Submission #497218

#	Time	Username	Problem	Language	Result	Execution time	Memory
497218		Gurban	Chessboard (IZhO18_chessboard)	C++17	100 / 100	1985 ms	12772 KiB

chessboard

#include <bits/stdc++.h>
using namespace std;

using ll = long long;

const int maxn=1e5+5;
int n,k;
int xl[maxn],yl[maxn];
int xr[maxn],yr[maxn];
vector<int>v[maxn],p[maxn];

bool col(int pos,int nw,int X){
	int now = pos / X;
	now %= 2;
	return now ^ nw;
}

ll f(int X,int tp){
	ll now = 0;
	int nw = tp ^ 1;
	for(int i = 0;i < n;i++){
		if(i % X == 0) nw ^= 1;

		if(nw) now += 1ll * (n / X + 1)/2 * X;
		else now += 1ll * (n/X) / 2 * X;	
	}

	nw = tp ^ 1;
	ll cnt[2]; cnt[0] = cnt[1] = 0;

	for(int i = 0;i < n;i++){
		if(i % X == 0){
			nw ^= 1;
			swap(cnt[0],cnt[1]);
		}
		for(auto j : v[i]){
			int z = xl[j] + (X - xl[j] % X);	
			if(z > xr[j]){
				int cl = col(xl[j],nw,X);
				cnt[cl] += (xr[j] - xl[j] + 1);
				continue;
			}
			if(z + X - 1 >= xr[j]){
				int cl = col(xl[j],nw,X);
				cnt[cl] += (z - xl[j]);

				cl = col(z,nw,X);
				cnt[cl] += (xr[j] - z + 1);
				continue;
			}
			int pos = xr[j] - (xr[j] % X); pos--;	
			
			int cl = col(xl[j],nw,X);
			cnt[cl] += (z - xl[j]);

			cl = col(xr[j],nw,X);
			cnt[cl] += (xr[j] - pos);
			
			cl = col(z,nw,X);
			cnt[cl] += ((pos-z+1)/X+1)/2*X;
			cnt[cl ^ 1] += ((pos-z+1)/X)/2*X;
		}

		// if(X == 2 and tp == 1) cout<<i<<' '<<cnt[0]<<' '<<cnt[1]<<'\n';

		now += cnt[0];
		now -= cnt[1];

		for(auto j : p[i]){
			int z = xl[j] + (X - xl[j] % X);	
			if(z > xr[j]){
				int cl = col(xl[j],nw,X);
				cnt[cl] -= (xr[j] - xl[j] + 1);
				continue;
			}
			if(z + X - 1 >= xr[j]){
				int cl = col(xl[j],nw,X);
				cnt[cl] -= (z - xl[j]);

				cl = col(z,nw,X);
				cnt[cl] -= (xr[j] - z + 1);
				continue;
			}
			int pos = xr[j] - (xr[j] % X); pos--;	
			
			int cl = col(xl[j],nw,X);
			cnt[cl] -= (z - xl[j]);

			cl = col(xr[j],nw,X);
			cnt[cl] -= (xr[j] - pos);
			
			cl = col(z,nw,X);
			cnt[cl] -= ((pos-z+1)/X+1)/2*X;
			cnt[cl ^ 1] -= ((pos-z+1)/X)/2*X;
		}
	}

	// cout<<X<<' '<<tp<<' '<<now<<'\n';

	return now;
}

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

	cin >> n >> k;
	for(int i = 1;i <= k;i++){
		cin >> xl[i] >> yl[i] >> xr[i] >> yr[i];
		xl[i]--,yl[i]--;
		xr[i]--,yr[i]--;
		v[yl[i]].push_back(i);
		p[yr[i]].push_back(i);
	}
	ll ans = 1ll * n * n;
	for(int i = 1;i < n;i++) if(n % i == 0){
		ans=min(ans,f(i,0));
		ans=min(ans,f(i,1));
	}
	cout<<ans;
}

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