Filter an Array

MediumPython

Problem

Array filtering: [1,1,2,3,3,4] → [1,1,3,3]

Asked in the Round 2: Technical + System Design (Tech Manager) stage. Coding challenge: keep only elements that appear more than once.

Task

Implement filter_repeated(nums) to return all occurrences of values whose total frequency is greater than one. Preserve the original order and do not modify nums.

Input and Output

Input: a list of integers nums.
Output: a new list containing only elements with frequency greater than one.

Constraints

0 <= len(nums) <= 10^5
-10^9 <= nums[i] <= 10^9
The input list must not be modified
Preserve the original order of retained elements

Function Signature

def filter_repeated(nums):

CodePython 3

Run your code to see test output here.