c++实现1.定义待排序表的长度为n。 2.初始化随机数发生器，产生n个随机数构成的顺序表。 3.创建输出排序表函数，取得系统时间函数，直接插入排序函数，冒泡排序函数，快速排序函数，直接选择排序函数，筛选函数，对排序函数，归并排序函数。 4.主程序调用各个排序函数，输出各排序算法对长度为n的顺序表进行排序所耗费的时间

下面是一份使用C++实现各种排序算法并测试时间的示例代码：

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <chrono>
using namespace std;
using namespace std::chrono;

// 直接插入排序
void insertSort(int arr[], int n) {
    for (int i = 1; i < n; i++) {
        int j = i;
        int tmp = arr[j];
        while (j > 0 && tmp < arr[j-1]) {
            arr[j] = arr[j-1];
            j--;
        }
        arr[j] = tmp;
    }
}

// 冒泡排序
void bubbleSort(int arr[], int n) {
    for (int i = 0; i < n-1; i++) {
        for (int j = 0; j < n-1-i; j++) {
            if (arr[j] > arr[j+1]) {
                swap(arr[j], arr[j+1]);
            }
        }
    }
}

// 快速排序
void quickSort(int arr[], int left, int right) {
    if (left >= right) return;
    int i = left, j = right, pivot = arr[left];
    while (i < j) {
        while (i < j && arr[j] >= pivot) j--;
        arr[i] = arr[j];
        while (i < j && arr[i] <= pivot) i++;
        arr[j] = arr[i];
    }
    arr[i] = pivot;
    quickSort(arr, left, i-1);
    quickSort(arr, i+1, right);
}

// 直接选择排序
void selectSort(int arr[], int n) {
    for (int i = 0; i < n-1; i++) {
        int minIdx = i;
        for (int j = i+1; j < n; j++) {
            if (arr[j] < arr[minIdx]) {
                minIdx = j;
            }
        }
        swap(arr[i], arr[minIdx]);
    }
}

// 筛选排序
void siftDown(int arr[], int i, int n) {
    int tmp = arr[i];
    while (2*i + 1 < n) {
        int j = 2*i + 1;
        if (j+1 < n && arr[j+1] > arr[j]) j++;
        if (tmp >= arr[j]) break;
        arr[i] = arr[j];
        i = j;
    }
    arr[i] = tmp;
}
void heapSort(int arr[], int n) {
    for (int i = n/2-1; i >= 0; i--) {
        siftDown(arr, i, n);
    }
    for (int i = n-1; i > 0; i--) {
        swap(arr[0], arr[i]);
        siftDown(arr, 0, i);
    }
}

// 归并排序
void merge(int arr[], int left, int mid, int right) {
    int n1 = mid - left + 1;
    int n2 = right - mid;
    int* L = new int[n1];
    int* R = new int[n2];
    for (int i = 0; i < n1; i++) {
        L[i] = arr[left+i];
    }
    for (int i = 0; i < n2; i++) {
        R[i] = arr[mid+1+i];
    }
    int i = 0, j = 0, k = left;
    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) {
            arr[k++] = L[i++];
        } else {
            arr[k++] = R[j++];
        }
    }
    while (i < n1) {
        arr[k++] = L[i++];
    }
    while (j < n2) {
        arr[k++] = R[j++];
    }
    delete[] L;
    delete[] R;
}
void mergeSort(int arr[], int left, int right) {
    if (left >= right) return;
    int mid = (left + right) / 2;
    mergeSort(arr, left, mid);
    mergeSort(arr, mid+1, right);
    merge(arr, left, mid, right);
}

// 输出数组
void printArr(int arr[], int n) {
    for (int i = 0; i < n; i++) {
        cout << arr[i] << " ";
    }
    cout << endl;
}

int main() {
    srand(time(NULL));
    int n;
    cout << "请输入待排序表的长度：";
    cin >> n;
    int* arr = new int[n];
    for (int i = 0; i < n; i++) {
        arr[i] = rand() % 100;
    }
    auto start = high_resolution_clock::now();
    insertSort(arr, n);
    auto stop = high_resolution_clock::now();
    cout << "直接插入排序用时：" << duration_cast<microseconds>(stop-start).count() << " us" << endl;
    start = high_resolution_clock::now();
    bubbleSort(arr, n);
    stop = high_resolution_clock::now();
    cout << "冒泡排序用时：" << duration_cast<microseconds>(stop-start).count() << " us" << endl;
    start = high_resolution_clock::now();
    quickSort(arr, 0, n-1);
    stop = high_resolution_clock::now();
    cout << "快速排序用时：" << duration_cast<microseconds>(stop-start).count() << " us" << endl;
    start = high_resolution_clock::now();
    selectSort(arr, n);
    stop = high_resolution_clock::now();
    cout << "直接选择排序用时：" << duration_cast<microseconds>(stop-start).count() << " us" << endl;
    start = high_resolution_clock::now();
    heapSort(arr, n);
    stop = high_resolution_clock::now();
    cout << "筛选排序用时：" << duration_cast<microseconds>(stop-start).count() << " us" << endl;
    start = high_resolution_clock::now();
    mergeSort(arr, 0, n-1);
    stop = high_resolution_clock::now();
    cout << "归并排序用时：" << duration_cast<microseconds>(stop-start).count() << " us" << endl;
    delete[] arr;
    return 0;
}

这份代码实现了6种排序算法，包括直接插入排序、冒泡排序、快速排序、直接选择排序、筛选排序、归并排序。在主程序中，我们先生成一个长度为n的随机数组，然后依次调用各个排序函数，计算每个函数的运行时间，并输出到屏幕上。