Submission #500346

#	Time	Username	Problem	Language	Result	Execution time	Memory
500346		dostigator	Chessboard (IZhO18_chessboard)	C++14	39 / 100	165 ms	8012 KiB

chessboard

// author lox:(
#pragma GCC optimize("O3")
#pragma GCC target("popcnt")
#include <bits/stdc++.h>
using namespace std;
#define IZhO_SILVER ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define popcnt __builtin_popcount
#define all(a) a.begin(),a.end()
#define low_b lower_bound
#define up_b upper_bound
#define vii vector<pair<ll,ll>>
#define vll vector<pair<ll,ll>>
#define pii pair<ll,ll>
#define mii map<ll,ll>
#define pll pair<ll,ll>
#define mll map<ll,ll>
#define vi vector<ll>
#define vl vector<ll>
#define pb push_back
#define endl '\n'
#define Y second
#define X first
typedef long double ld;
typedef long long ll;
const long long dx[4]={1,-1,0,0},dy[4]={0,0,1,-1},col=107,N=1e6+777;
const ll mod=1e9+7,inf=1e18;
void fre_open(){freopen("file.in","r",stdin);freopen("file.out","w",stdout);}
ll binpow(ll n,ll k){if(k<0)return 0ll;if(k==0)return 1ll;if(k%2)return (binpow(n,k-1)*n)%mod;ll kk=binpow(n,k/2)%mod;return (kk*kk)%mod;}
int a[2001][2001];
int n,k;
bool isprime(long long x)
{
	if(x < 2) return 0;
	if(x == 2 || x == 3) return 1;
	if(x % 2 == 0 || x % 3 == 0) return 0;
	for(int i = 5; i * i <= n; i += 6)
		if(x % i == 0 || x % (i+2) == 0)
			return 0;
	return 1;
}
void f2()
{
	int x = n*n/2;
	int x2 = x + 1;
	for(int c = 0, i1, i2, j1, j2; c < k; ++c)
	{
		cin >> i1 >> j1 >> i2 >> j2;
		for(int i = i1; i <= i2; ++i)
			for(int j = j1; j <= j2; ++j)
			{
				if(i % 2 == j % 2) x++, x2--;
				if(i % 2 != j % 2) x2++, x--;
			}
	}

	cout << min(x, x2);
}
void solve(){
    cin>>n>>k;
    if(k==0){
        int x=n*n/2;
        for(int i=n/2; i>=1; --i)if(n%i==0)x=min(x,i*i*((n/i)*(n/i)/2));
        cout<<x;
        return;
    }
    else if(isprime(n)) {f2();return;}
    for(int i=1; i<=k; ++i){
        ll x,y,tox,toy;
        cin>>x>>y>>tox>>toy;
        a[x][y]=1;
    }
    int ans=mod-10;
    for(int d=1; d*d<=n; ++d){
        if(n%d!=0) continue;
        int res=0,res2=0;
        for(int i=1; i<=n; ++i){
            for(int j=1; j<=n; ++j){
                int x=(i+(d-1))/d;
                int y=(j+(d-1))/d;
                if((x+y)%2 && a[i][j]) ++res2;
                if((x+y)%2 && !a[i][j]) ++res;
                if(!((x+y)%2) && a[i][j]) ++res;
                if(!((x+y)%2) && !a[i][j]) ++res2;
            }
        }
        ans=min({ans,res,res2});
        //cout<<d<<' '<<res<<' '<<res2<<endl;
        int f=n/d;
        res=0,res2=0;
        for(int i=1; i<=n; ++i){
            for(int j=1; j<=n; ++j){
                int x=(i+(f-1))/f;
                int y=(j+(f-1))/f;
                if((x+y)%2 && a[i][j]) ++res2;
                if((x+y)%2 && !a[i][j]) ++res;
                if(!((x+y)%2) && a[i][j]) ++res;
                if(!((x+y)%2) && !a[i][j]) ++res2;
            }
        }
        if(d==1){
            ans=min(ans,max(res,res2));
            continue;
        }
        ans=min({ans,res,res2});
        //cout<<d<<' '<<res<<' '<<res2<<endl;
    }
    cout<<ans<<endl;
}
/*
6 8
3 3 3 3
1 2 1 2
3 4 3 4
5 5 5 5
4 3 4 3
4 4 4 4
2 1 2 1
3 6 3 6*/
int main() {
    //fre_open();
    IZhO_SILVER;
    ll tt=1;
    //cin>>tt;
    while(tt--) solve();
}

Compilation message (stderr)

chessboard.cpp: In function 'void fre_open()':
chessboard.cpp:27:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 | void fre_open(){freopen("file.in","r",stdin);freopen("file.out","w",stdout);}
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
chessboard.cpp:27:53: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 | void fre_open(){freopen("file.in","r",stdin);freopen("file.out","w",stdout);}
      |                                              ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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