最接近神的人(Closest to God) 题解

思路分析

按题目要求使用对应数据结构与算法模拟/递推求解，注意数据范围边界与时间复杂度。

参考代码

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    if (!(cin >> n)) return 0;
    vector<long long> a(n), vals(n);
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
        vals[i] = a[i];
    }
    sort(vals.begin(), vals.end());
    vals.erase(unique(vals.begin(), vals.end()), vals.end());
    int m = (int)vals.size();
    vector<int> bit(m + 1, 0);
    auto add = [&](int idx) {
        for (int i = idx; i <= m; i += i & -i) ++bit[i];
    };
    auto query = [&](int idx) {
        int s = 0;
        for (int i = idx; i > 0; i -= i & -i) s += bit[i];
        return s;
    };
    long long ans = 0;
    for (int i = 0; i < n; ++i) {
        int rk = (int)(lower_bound(vals.begin(), vals.end(), a[i]) - vals.begin()) + 1;
        ans += i - query(rk);
        add(rk);
    }
    cout << ans << "\n";
    return 0;
}