Non-unique Elements
You are given a non-empty list of integers (X). For this task, you should return a list consisting of only the non-unique elements in this list. To do so you will need to remove all unique elements (elements which are contained in a given list only once). When solving this task, do not change the order of the list. Example: [1, 2, 3, 1, 3] 1 and 3 non-unique elements and result will be [1, 3, 1, 3].
Examples
| Input | Output |
|---|---|
[1, 2, 3, 1, 3] | [1, 3, 1, 3] |
[1, 2, 3, 4, 5] | [] |
[5, 5, 5, 5, 5] | [5, 5, 5, 5, 5] |
[10, 9, 10, 10, 9, 8] | [10, 9, 10, 10, 9] |
Solution
/ζ(\d+)(.*)ζ\1/ζ$1$2λ$1/ /ζ(\d+)(.*)λ\1/λ$1$2λ$1/ /ζ(\d+)(, )?// /, ]/]/ /[ζλ]//g ! /(\d+)/ζ$1/g