排序算法

1.堆排序

void sift(vector<int> &arr, int low, int high)
{
    int i = low, j = 2 * i;
    int temp = arr[i];
    while (j <= high)
    {
        if (j < high && arr[j] < arr[j + 1]) {
            j++;
        }
        if (temp < arr[j]) {
            arr[i] = arr[j];
            i = j;
            j = 2 * i;
        }
        else {
            break;
        }
    }
    arr[i] = temp;
}

void heapSort(vector<int> &arr)
{
    int n = arr.size() - 1;

    if (n <= 1) {
        return;
    }

    for (int i = n / 2; i >= 1; i--)
    {
        sift(arr, i, n);
    }

    for (int i = n; i >= 2 ; i--)
    {
        swap(arr[1], arr[i]);
        sift(arr, 1, i - 1);
    }

}

测试用例:

有效排序元素从1开始

vector<int> arr = {0, 3, 2, 4, 1, 7, 6 };

heapSort(arr);