Python Script To Remove Unique Elements From A List And Print The List With Repeated Elements In Proper Order
I have written a script to remove all unique elements from a list and print the list with only repeated elements: Below are some examples how the output list for an input list shou
Solution 1:
your script has a number of issues:
- the classical
if x in dict1.keys()
=>if x in dict1
to be sure to use the dictionary check instead of linear - no list comprehension:
append
in a loop, not as performant. O(n^2)
complexity because of the double loop
My approach:
You could count your elements using collections.Counter
, then filter out a new list using a list comprehension using a filter on the number of ocurrences:
from collections import Counter
list1 = [1,2,1,1,3,5,3,4,3,1,6,7,8,5]
c = Counter(list1)
new_list1 = [k for k in list1 if c[k]>1]
print(new_list1)
result:
[1, 1, 1, 3, 5, 3, 3, 1, 5]
I may be wrong but, the complexity of this approach is (roughly) O(n*log(n))
(linear scan of the list plus the hashing of the keys in the dictionary and the lookup in the list comprehension). So, it's good performance-wise.
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