Submission #1224375

#	Time	Username	Problem	Language	Result	Execution time	Memory
1224375		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 Fenwick {
    int n;
    vector<ll> f;
    Fenwick(int _n): n(_n), f(n+2, 0) {}
    void update(int i, ll v) {
        for (; i <= n; i += i & -i) f[i] += v;
    }
    ll query(int i) {
        ll res = 0;
        for (; i > 0; i -= i & -i) res += f[i];
        return res;
    }
};

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

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

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

    int M = vals.size();
    Fenwick bit(M + 2);

    ll ans = 0;
    for (int i = 0; i < N; ++i) {
        int pos = lower_bound(vals.begin(), vals.end(), B[i]) - vals.begin() + 1;
        ans += i - bit.query(pos);
        bit.update(pos, 1);
    }

    cout << ans ;
    return 0;
}

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