希尔排序

# -*- coding: utf-8 -*-
def shell_sort(alist):
    """希尔排序"""
    #n=9
    n=len(alist)
    #gap=4
    gap= n//2
    # gap变化到0之前，插入算法执行的次数
    while gap>=1:
            #插入算法，与普通的插入算法的区别就是gap步长
        for j in range(gap,n):
            # j =[gap,gap+1,gap+2,....,n-1]
            i=j
            while i>0:
                if alist[i]<alist[i-gap]:
                    alist[i],alist[i-gap]=alist[i-gap],alist[i]
                    i-=gap
                else:
                    break
        # 缩短gap步长
        gap//=2
if __name__ == ‘__main__‘:
    li = [54,26,93,17,77,31,44,55,20]
    print(li)
    shell_sort(li)
    print(li)