Heap sort (c#)

heap sort

Steps for heap sort:

1. Construct the array into a large root heap, at this time the top element of the heap is the largest element in the array
2. Exchange the top element of the heap with the end element, and the maximum value of the array has been obtained at this time
3. Repeat steps 1 and 2 for the remaining n-1 elements, and finally get an ordered array.

Heap sort implementation code:

/// <summary>
/// 堆排序
/// </summary>
/// <param name="nums"></param>
static void SortByHeap(int[] nums)
{
    //构造大根堆 从最后一个非叶子节点开始
    int len = nums.Length;
    for (int i = len / 2 - 1; i >= 0; i--)
    {
        AdjustHeap(nums, i, len);
    }

    //调整堆
    for (int i = len - 1; i > 0; i--)
    {
        //交换堆顶元素与末尾元素，得到当前i+1长度中的最大值
        (nums[0], nums[i]) = (nums[i], nums[0]);
        //剩余的i长度的元素继续构造大根堆
        AdjustHeap(nums, 0, i);
    }

}

/// <summary>
/// 调整堆
/// </summary>
/// <param name="nums"></param>
/// <param name="begin">开始下标</param>
/// <param name="length">调整长度</param>
static void AdjustHeap(int[] nums, int begin, int length)
{
    int temp = nums[begin];
    for (int i = 2 * begin + 1; i < length; i = 2 * i + 1)
    {
        if (i + 1 < length && nums[i + 1] > nums[i]) i++;
        if (nums[i] > temp)
        {
            nums[begin] = nums[i];
            begin = i;
        }
        else
        {
            break;
        } 
    }

    nums[begin] = temp;
}