14.排序算法（5）

1.堆排序介绍

构建大顶堆或者小顶堆（大顶堆用于升序，小顶堆用于降序）
交换最后一个叶子结点和根结点
调整根结点，使无序区重新变成大顶堆

2. 代码实现

def big_endian(lst, start, end):
    root = start
    while True:
        child = root * 2 + 1
        if child > end:
            break
        if child + 1 <= end and lst[child] < lst[child + 1]:
            child += 1
        if lst[root] < lst[child]:
            lst[root], lst[child] = lst[child], lst[root]
            root = child
        else:
            break


def heap_sort(lst):
    first = len(lst) // 2 - 1
    for start in range(first, -1, -1):
        big_endian(lst, start, len(lst) - 1)
    for end in range(len(lst) - 1, 0, -1):
        lst[0], lst[end] = lst[end], lst[0]
        big_endian(lst, 0, end - 1)

if __name__ == "__main__":
    l = [3, 1, 4, 9, 6, 7, 5, 8, 2, 10]
    print(l)
    heap_sort(l)
    print(l)

# 运行结果
[3, 1, 4, 9, 6, 7, 5, 8, 2, 10]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]