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题目：给定一个长度为2n的序列，要求奇数位放奇数，偶数位放偶数

解题：双指针，分别按步长2进行走，当同时偶数位遇到奇数，奇数位遇到偶数时，进行交换，指针均向后移动

算法代码

#!/usr/bin/env python
# -*- coding: utf-8 -*-

def oddsort(data):
 size = len(data)
 if not data or size < 2:
 return data
 
 odd = even = 0
 for i in data:
 if i % 2 == 0:
 even += 1
 else:
 odd += 1

 if odd != even:
 return '序列奇数偶数数量不同，无法排序'

 i = 0
 j = 1

 while True:
 while i < size and data[i] % 2 == 0:
 i += 2

 while j < size and data[j] % 2 != 0:
 j += 2

 if i >= size or j >= size:
 break

 tmp = data[i]
 data[i] = data[j]
 data[j] = tmp

 i += 2
 j += 2

 return data

# 测试用例
data = []
print(oddsort(data))
data = [2,1,7,12,9]

print(oddsort(data))
data1 = [2,1,7,12,6,9]

print(oddsort(data1))
data2 = [2,1,7,12,9,6]
print(oddsort(data2))


# 输出
[]
序列奇数偶数数量不同，无法排序
[2, 1, 12, 7, 6, 9]
[2, 1, 12, 7, 6, 9]