算法-算法练习(shell排序和归并排序)

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# 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

  

posted on   cloud_wh  阅读(441)  评论(0编辑  收藏  举报

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