用c++语言写以下程序：求逆序对的数目

以下是使用归并排序求逆序对数目的 C++ 代码：

#include <iostream>
using namespace std;

long long merge(int arr[], int temp[], int left, int mid, int right) {
    long long count = 0;
    int i = left, j = mid, k = left;
    while (i <= mid - 1 && j <= right) {
        if (arr[i] <= arr[j])
            temp[k++] = arr[i++];
        else {
            temp[k++] = arr[j++];
            count += mid - i;
        }
    }
    while (i <= mid - 1)
        temp[k++] = arr[i++];
    while (j <= right)
        temp[k++] = arr[j++];
    for (i = left; i <= right; i++)
        arr[i] = temp[i];
    return count;
}

long long mergeSort(int arr[], int temp[], int left, int right) {
    long long count = 0;
    if (left < right) {
        int mid = (left + right) / 2;
        count += mergeSort(arr, temp, left, mid);
        count += mergeSort(arr, temp, mid + 1, right);
        count += merge(arr, temp, left, mid + 1, right);
    }
    return count;
}

long long countInversions(int arr[], int n) {
    int temp[n];
    return mergeSort(arr, temp, 0, n - 1);
}

int main() {
    int n;
    cout << "Enter the number of elements: ";
    cin >> n;
    int arr[n];
    cout << "Enter the elements: ";
    for (int i = 0; i < n; i++)
        cin >> arr[i];
    long long inversions = countInversions(arr, n);
    cout << "Number of inversions: " << inversions << endl;
    return 0;
}

输入格式为：第一行输入元素个数 n，第二行输入 n 个元素。输出逆序对的数目。