数据结构学习（shell排序和归并排序）

# coding=utf-8

# shell排序
# 参数alist：被被排序的列表
def shellsort(alist):

    gap = len(alist) / 2

    while gap > 0:

        for i in range(gap):
            shellinsert(alist, i, gap)

        gap = gap / 2

        print alist

#根据步长进行插入排序
def shellinsert(alist, start, gap):

    for i in range(start + gap, len(alist), gap):
        temp = alist[i]
        position = i

        while position >= gap and alist[position - gap] > temp:
            alist[position] = alist[position - gap]
            position = position - gap
        alist[position] = temp

# 归并排序
# 参数alist：被被排序的列表
def mege_sort(alist):
    if len(alist) <= 1:
        return alist

    num = int(len(alist) / 2)

    leftList = mege_sort(alist[:num])
    rightList = mege_sort(alist[num:])

    return mege(leftList, rightList)

#将两个列表合并为一个列表进行返回
def mege(leftList, rightList):
    l = 0
    r = 0

    result = []

    while l < len(leftList) and r < len(rightList):
        if leftList[l] < rightList[r]:
            result.append(leftList[l])
            l += 1
        else:
            result.append(rightList[r])
            r += 1

    result = result + leftList[l:]
    result = result + rightList[r:]

    return result

alist = [9, 8, 9, 9, 7, 6, 5, 4, 3, 2, 1]

if __name__ == '__main__':
    # shellsort(alist)

    result = mege_sort(alist)

    print alist
    print result