用c++使用函数模板实现任意类型的数组的降序排序。

好的，可以参考下面的代码实现：

#include <iostream>
using namespace std;

template <typename T>
void selectionSort(T arr[], int n) {
    for (int i = 0; i < n - 1; i++) {
        int maxIndex = i;
        for (int j = i + 1; j < n; j++) {
            if (arr[j] > arr[maxIndex]) {
                maxIndex = j;
            }
        }
        swap(arr[i], arr[maxIndex]);
    }
}

int main() {
    int intArr[] = { 3, 6, 1, 9, 2 };
    double doubleArr[] = { 3.5, 6.8, 1.2, 9.6, 2.7 };
    char charArr[] = { 'c', 'b', 'a', 'e', 'd' };
    int n = 5;

    cout << "Original int array: ";
    for (int i = 0; i < n; i++) {
        cout << intArr[i] << " ";
    }
    selectionSort(intArr, n);
    cout << "\nSorted int array: ";
    for (int i = 0; i < n; i++) {
        cout << intArr[i] << " ";
    }

    cout << "\nOriginal double array: ";
    for (int i = 0; i < n; i++) {
        cout << doubleArr[i] << " ";
    }
    selectionSort(doubleArr, n);
    cout << "\nSorted double array: ";
    for (int i = 0; i < n; i++) {
        cout << doubleArr[i] << " ";
    }

    cout << "\nOriginal char array: ";
    for (int i = 0; i < n; i++) {
        cout << charArr[i] << " ";
    }
    selectionSort(charArr, n);
    cout << "\nSorted char array: ";
    for (int i = 0; i < n; i++) {
        cout << charArr[i] << " ";
    }

    return 0;
}

这里定义了一个函数模板 `selectionSort`，可以对任意类型的数组进行降序排序。在主函数中，我们分别定义了整型、双精度浮点型和字符型数组，并通过函数模板 `selectionSort` 对它们进行排序。