Submission #495180

#	Time	Username	Problem	Language	Result	Execution time	Memory
495180		armashka	Chessboard (IZhO18_chessboard)	C++17	39 / 100	74 ms	3320 KiB

chessboard

#include <bits/stdc++.h>
 
//#pragma comment(linker, "/stack:200000000")
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
 
#define fast ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
#define all(v) v.begin(),v.end()
#define pb push_back
#define sz size()
#define ft first
#define sd second
 
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef unsigned long long ull;
 
const int N = 1e6 + 5;
const ll M = 1e8;
const ll inf = 1e9;
const ll mod = 1e9;
const double Pi = acos(-1); 
 
ll binpow(ll x, ll ti) { ll res = 1;while (ti){if(ti & 1)res *= x;x *= x;ti >>= 1; x %= mod; res %= mod;} return res;}
ll binmul(ll x, ll ti) { ll res = 0;while (ti){if(ti & 1)res += x;x += x;ti >>= 1; x %= mod; res %= mod;} return res;}
ll nok(ll a, ll b) { return (a*b)/__gcd(abs(a),abs(b)) * (a*b > 0 ? 1 : -1); }
bool odd(ll n) { return (n % 2 == 1); }
bool even(ll n) { return (n % 2 == 0); }            
                     
struct node {
	ll x1, y1, x2, y2;
};
                                               
ll n, k, ans = inf;
bool bl[1005][1005];
node que[100005]; 
 
void check(int razmer) {
	ll cnt = 0;
	for (int i = 1; i <= n; ++ i) {
		for (int j = 1; j <= n; ++ j) {
			int num = ((i + razmer - 1) / razmer) + ((j + razmer - 1) / razmer);
			if (even(num) && !bl[i][j]) ++ cnt;
			if (odd(num) && bl[i][j]) ++ cnt; 
		}
	}
	//cout << razmer << " " << min(cnt, n * n - cnt) << "\n";
	ans = min(ans, min(cnt, n * n - cnt));
	return;
}
 
const void solve(/*Armashka*/) {
	cin >> n >> k;
	ll c1 = (n * n) / 2, c2 = (n * n) - c1, cnt1 = 0, cnt2 = 0;
	bool ok = 1;
	for (int i = 1; i <= k; ++ i) {
		ll x1, y1, x2, y2;
		cin >> x1 >> y1 >> x2 >> y2;
		que[i] = {x1, y1, x2, y2};
		if (x1 % 2 == y1 % 2) ++ cnt2;
		else ++ cnt1;
		if (x1 != x2 || y1 != y2) ok = 0;
	}
	if (ok) {
		vector <ll> v;
		for (int i = 1; i * i <= n; ++ i) {
			if (n % i == 0) {
				v.pb(i);
				if (n / i != i && i > 1) v.pb(n / i);
			}
		}
		for (int j = 0; j < v.sz; ++ j) {
			ll cnt1 = 0, cnt2 = 0;
			for (int i = 1; i <= k; ++ i) {                                                       
				ll num = (que[i].x1 + v[j] - 1) / v[j] + (que[i].y1 + v[j] - 1) / v[j];
				if (odd(num)) ++ cnt1;
				else ++ cnt2;
			}
			//cout << v[j] << " " << (n * n / (v[j] * v[j])) << " " << cnt1 << " " << cnt2 << "\n";
			ll col = ((n * n) / (v[j] * v[j])) / 2; col *= v[j] * v[j];
			ll res = col - cnt1 + cnt2;
			ans = min(ans, min(res, n * n - res));
		}
		cout << ans << "\n";
		return;
	}
	for (int i = 1; i <= k; ++ i) {
		for (int j = que[i].x1; j <= que[i].x2; ++ j) {
			for (int h = que[i].y1; h <= que[i].y2; ++ h) bl[j][h] = 1;
		}
	}
	for (int i = 1; i * i <= n; ++ i) {
		if (n % i == 0) {
			check(i);
			if (n / i != i && i > 1) check(n / i);
		}
	}
	cout << ans << "\n";
}
 
signed main() {
    fast;
	//freopen("divide.in", "r", stdin);
	//freopen("divide.out", "w", stdout);
    int tt = 1;
    //cin >> tt;
    while (tt --) {
    	solve();
	}
}
 
/*
 
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
 
*/
 
/*
9 12
1 9 4
1 2 5
2 3 7
2 4 3
4 3 6
3 6 4
8 7 10
6 7 5
5 8 1
9 5 7
5 4 12
6 8 2
2
4 7
5
1 6
5 3
4 8
5 8
1 5
 
*/

Compilation message (stderr)

chessboard.cpp: In function 'const void solve()':
chessboard.cpp:73:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   73 |   for (int j = 0; j < v.sz; ++ j) {
      |                     ^
chessboard.cpp:55:23: warning: unused variable 'c2' [-Wunused-variable]
   55 |  ll c1 = (n * n) / 2, c2 = (n * n) - c1, cnt1 = 0, cnt2 = 0;
      |                       ^~

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