Find duplicates in an array FASTEST Python Solution Geeksforgeeks POTD
Given an array a of size N which contains elements from 0 to N-1, you need to find all the elements occurring more than once in the given array. Return the answer in ascending order. If no such element is found, return list containing [-1]
Note: The extra space is only for the array to be returned. Try and perform all operations within the provided array