利用Python实现归并排序

利用python进行归并排序，摘抄自http://blog.csdn.net/minxihou/article/details/51821052

“代码真的不是一气呵成的，而且也不是想当然写出来的。可能需要反复断点中断来查看是否有逻辑错误。在理解了问题的基础下我们需要先把大体的代码框架最好先写出来，
特别是主要的逻辑判断语句。但是不需要太care我循环体或者判断里面语句怎么实现，当你把这一步做到的时候能避免很多不必要的错误发生。”

import random

def ConfiationAlgorithm(str):
    if len(str) <= 1: #子序列
        return str
    mid = (len(str) // 2)
    left = ConfiationAlgorithm(str[:mid])#递归的切片操作
    right = ConfiationAlgorithm(str[mid:])
    result = []
    #i,j = 0,0

    while len(left) > 0 and len(right) > 0:
        if (left[0] <= right[0]):
            #result.append(left[0])
            result.append(left.pop(0))
            #i+= 1
        else:
            #result.append(right[0])
            result.append(right.pop(0))
            #j+= 1

    if (len(left) > 0):
        result.extend(ConfiationAlgorithm(left))
    else:
        result.extend(ConfiationAlgorithm(right))
    return result

if __name__ == '__main__':
    a = [20,30,64,16,8,0,99,24,75,100,69]
    print(ConfiationAlgorithm(a))
    b = [random.randint(1,1000) for i in range(10)]
    print(ConfiationAlgorithm(b))

另一种思路

def merge(left, right):
    i, j = 0, 0
    result = []
    while i < len(left) and j < len(right):
        if left[i] <= right[j]:
            result.append(left[i])
            i += 1
        else:
            result.append(right[j])
            j += 1
    result += left[i:]
    result += right[j:]
    return result

def merge_sort(lists):
    # 归并排序
    if len(lists) <= 1:
        return lists
    num = len(lists) / 2
    left = merge_sort(lists[:num])
    right = merge_sort(lists[num:])
    return merge(left, right)