code/MeiTuan2/question5.cpp

#include<iostream>
#include<vector>
using namespace std;
const int N=200000;
void merge__(vector<int>& arr, vector<int>& tmp, int l, int mid, int r, int& ret) {
    int i = l, j = mid + 1, k = 0;

    while (i <= mid && j <= r) {
        if (arr[i] > arr[j]) {
            tmp[k++] = arr[j++];
            ret += (mid - i + 1);
        }
        else {
            tmp[k++] = arr[i++];
        }
    }
    while (i <= mid) {
        tmp[k++] = arr[i++];
    }
    while (j <= r) {
        tmp[k++] = arr[j++];
    }

    for (k = 0, i = l; i <= r; ++i, ++k) {
        arr[i] = tmp[k];
    }
}
void merge_sort__(vector<int>& arr, vector<int>& tmp, int l, int r, int& ret) {
    if (l >= r) {
        return;
    }

    int mid = l + ((r - l) >> 1);
    merge_sort__(arr, tmp, l, mid, ret);
    merge_sort__(arr, tmp, mid + 1, r, ret);
    merge__(arr, tmp, l, mid, r, ret);
}

int InversePairs(vector<int>& nums) {
    // write code here
    int ret = 0;
    // 在最外层开辟数组
    vector<int> tmp(nums.size());
    merge_sort__(nums, tmp, 0, nums.size() - 1, ret);
    return ret;
}

int main()
{
    vector<int> q;
    int n,a;
    cin >> n;
    int result;
    for(int i=0;i<n;i++){
        cin >>a;
        q.push_back(a);
    } 
    for(int i=0;i<n;i++){
        q[i] = -q[i];
        result = InversePairs(q);
        cout << result<< ' ';
        q[i] = -q[i];
    }
    
    return 0;
}