python - 排列排序列表中的元素，使所有冗余元素位于列表的左侧/右侧

Question

有没有比这个更好的方法来解决这个问题？
def 渲染(arr):

single_elements = []  
double_elements = []  

for i in xrange(len(arr)-1):  
    if arr[i] == arr[i+1] or arr[i] == arr[i-1]:  
        double_elements.append(arr[i])  
    else:  
        single_elements.append(arr[i])

if arr[-1] == double_elements[-1]:
    double_elements.append(arr[-1])
else: 
    single_elements.append(arr[-1])

return single_elements+double_elements

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

'''输出 arr = [1,2,4,5,6,9,3,3,3,7,7,7,7,8,8,8]'''

打印渲染(arr)

Answer 1

你不能在一行中很好地完成它，但我认为最好保留它 O(N)

>>> from itertools import groupby
>>> arr = [1,2,3,3,3,4,5,6,7,7,7,7,8,8,8,9]
>>> a, b = [], []
>>> for k, g in groupby(arr):
        group = list(g)
        (a if len(group)<2 else b).extend(group)


>>> print a + b
[1, 2, 4, 5, 6, 9, 3, 3, 3, 7, 7, 7, 7, 8, 8, 8]