Submission #878077

#	Time	Username	Problem	Language	Result	Execution time	Memory
878077		The_Samurai	Chessboard (IZhO18_chessboard)	C++17	100 / 100	699 ms	11600 KiB

chessboard

#include "bits/stdc++.h"
using namespace std;
using ll = long long;
const ll inf = 1e18;

struct Fenwick {
    vector<int> tree;
    int n;

    void init(int len) {
        n = len;
        tree.assign(n + 1, 0);
    }

    void update(int i, int v) {
        i++;
        while (i <= n) {
            tree[i] += v;
            i += i & (-i);
        }
    }

    int get(int i) {
        i++;
        int sum = 0;
        while (i > 0) {
            sum += tree[i];
            i -= i & (-i);
        }
        return sum;
    }

    int get(int l, int r) {
        return get(r) - get(l - 1);
    }
};

void solve() {
    int n, k;
    cin >> n >> k;
    vector<vector<pair<int, int>>> in(n + 1), out(n + 1);
    for (int i = 0; i < k; i++) {
        int x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;
        in[x1].emplace_back(y1, y2);
        out[x2].emplace_back(y1, y2);
    }
    vector<int> del;
    for (int i = 1; i * i <= n; i++) {
        if (n % i) continue;
        del.emplace_back(i);
        if (i != 1 and i * i != n) del.emplace_back(n / i);
    }
    auto get_black = [&](int x, int p) -> int {
        if (x == 0) return 0;
        int ans = (x - 1) / (2 * p) * p;
        int md = (x - 1) % (2 * p);
        ans += min(p, md + 1);
        return ans;
    };
    auto get_white = [&](int x, int p) -> int {
        if (x == 0) return 0;
        int ans = (x - 1) / (2 * p) * p;
        int md = (x - 1) % (2 * p);
        if (md + 1 > p) ans += md + 1 - p;
        return ans;
    };
    auto color = [&](int x, int p) -> int {
        int md = (x - 1) % (2 * p);
        return md < p;
    };
    ll ans = 1e18;
    for (int p: del) {
        int b_size = get_black(n, p), w_size = get_white(n, p);
//        cout << p << ' ' << b_size << ' ' << w_size << endl;
        for (int s = 0; s < 2; s++) {
            ll need = 0;
            int bib = 0, biw = 0;
            for (int i = 1; i <= n; i++) {
                for (auto [l, r]: in[i]) {
                    int cnt = get_black(r, p) - get_black(l, p) + color(l, p);
                    bib += cnt;
                    biw += (r - l + 1) - cnt;
                }
                int wib = b_size - bib;
                int wiw = w_size - biw;

                bool wh = true;
                if ((i - 1) / p % 2 == 0) wh = !wh;
                if (s) wh = !wh;
                need += wh ? biw + wib : bib + wiw;

                for (auto [l, r]: out[i]) {
                    int cnt = get_black(r, p) - get_black(l, p) + color(l, p);
                    bib -= cnt;
                    biw -= (r - l + 1) - cnt;
                }
            }
//            cout << p << ' ' << s << ' ' << need << endl;
            ans = min(ans, need);
        }
    }
    cout << ans;

}

int main() {
    cin.tie(0)->sync_with_stdio(false);
#ifdef sunnatov
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    int queries = 1;
//    cin >> queries;

    for (int test_case = 1; test_case <= queries; test_case++) {
#ifdef sunnatov
        cout << "Test case: " << test_case << endl;
#endif
        solve();
        cout << '\n';
    }
}

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