Submission #1224379

#	Time	Username	Problem	Language	Result	Execution time	Memory
1224379		vipul	Group Photo (JOI21_ho_t3)	C++20	0 / 100	0 ms	320 KiB

Main

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

struct BIT {
    vector<int> bit;
    int n;

    BIT(int n) {
        this->n = n;
        bit.assign(n + 1, 0);
    }

    void add(int idx, int val) {
        while (idx <= n) {
            bit[idx] += val;
            idx += idx & -idx;
        }
    }

    int sum(int idx) {
        int res = 0;
        while (idx > 0) {
            res += bit[idx];
            idx -= idx & -idx;
        }
        return res;
    }
};

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

    int N;
    cin >> N;
    vector<ll> A(N), transformed(N);
    for (int i = 0; i < N; ++i) {
        cin >> A[i];
        transformed[i] = A[i] - 2LL * i;
    }

    // Coordinate compression
    vector<ll> sorted = transformed;
    sort(sorted.begin(), sorted.end());
    sorted.erase(unique(sorted.begin(), sorted.end()), sorted.end());

    int size = sorted.size();
    BIT bit(size);

    ll ans = 0;
    for (int i = N - 1; i >= 0; --i) {
        int pos = lower_bound(sorted.begin(), sorted.end(), transformed[i]) - sorted.begin() + 1;
        ans += bit.sum(pos - 1);
        bit.add(pos, 1);
    }

    cout << ans << "\n";
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 7
• Subtask 3: 0 / 32
• Subtask 4: 0 / 20
• Subtask 5: 0 / 36