Submission #946009

#	Time	Username	Problem	Language	Result	Execution time	Memory
946009		itslq	Road Construction (JOI21_road_construction)	C++17	0 / 100	10095 ms	352360 KiB

road_construction

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

#define int long long

int N, K, X, Y;
vector<int> x, y;
unordered_map<int, int> fenwick;

int enc(int a, int b) {
    return a * 1e6 + b;
}

void update(int i, int j1, bool b) {
    for (; i <= X; i += i & -i) {
        for (int j = j1; j <= Y; j += j & -j) {
            if (b) fenwick[enc(i, j)]++;
            else fenwick[enc(i, j)]--;
        }
    }
}

int query(int i, int j1) {
    int S = 0;
    for (; i > 0; i -= i & -i) {
        for (int j = j1; j > 0; j -= j & -j) {
            S += fenwick[enc(i, j)];
        }
    }
    return S;
}

bool check(int d) {
    int x1, y1, S = 0, ia, ib, ic, id;

    vector<int> xdisc, ydisc;

    for (int i = 0; i < N; i++) {
        x1 = x[i];
        y1 = y[i];

        xdisc.push_back(x1 - y1 - d);
        xdisc.push_back(x1 - y1);
        xdisc.push_back(x1 - y1 + d);
        ydisc.push_back(x1 + y1 - d);
        ydisc.push_back(x1 + y1);
        ydisc.push_back(x1 + y1 + d);
    }

    sort(xdisc.begin(), xdisc.end());
    sort(ydisc.begin(), ydisc.end());

    xdisc.erase(unique(xdisc.begin(), xdisc.end()), xdisc.end());
    ydisc.erase(unique(ydisc.begin(), ydisc.end()), ydisc.end());

    X = xdisc.size();
    Y = ydisc.size();
    fenwick = unordered_map<int, int>();

    for (int i = 0; i < N; i++) {
        x1 = x[i];
        y1 = y[i];

        ia = lower_bound(xdisc.begin(), xdisc.end(), x1 - y1) - xdisc.begin() + 1;
        ib = lower_bound(ydisc.begin(), ydisc.end(), x1 + y1) - ydisc.begin() + 1;

        if ((S += query(ia, ib)) >= K) return true;

        ia = lower_bound(xdisc.begin(), xdisc.end(), x1 - y1 - d) - xdisc.begin() + 1;
        ib = lower_bound(xdisc.begin(), xdisc.end(), x1 - y1 + d) - xdisc.begin() + 1;
        ic = lower_bound(ydisc.begin(), ydisc.end(), x1 + y1 - d) - ydisc.begin() + 1;
        id = lower_bound(ydisc.begin(), ydisc.end(), x1 + y1 + d) - ydisc.begin() + 1;

        update(ia, ic, 1);
        update(ib + 1, ic, 0);
        update(ia, id + 1, 0);
        update(ib + 1, id + 1, 1);
    }

    return false;
}

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> N  >> K;
    x.resize(N);
    y.resize(N);
    for (int i = 0; i < N; i++) cin >> x[i] >> y[i];

    int l = 0, r = 4e9, m, ans;
    while (l <= r) {
        m = (l + r) >> 1;
        if (check(m)) {
            ans = m;
            r = --m;
        } else {
            l = ++m;
        }
    }

    cout << ans;
    return 0;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 6
• Subtask 3: 0 / 7
• Subtask 4: 0 / 20
• Subtask 5: 0 / 27
• Subtask 6: 0 / 35