Repeated Elements in an Array

Write a method duplicate to find the repeated or duplicate elements in an array.
This method should return a list of repeated integers in a string with the elements sorted in ascending order (as illustrated below).

duplicate({1,3,4,2,1}) --> "[1]"

duplicate({1,3,4,2,1,2,4}) --> "[1, 2, 4]"

Note: You may use toString() method to return the
standard string representation of most data structures, and
Arrays.sort() to sort your result.

Need a hand? Try out these hints, one at a time.

Quick hint to get things rolling

If you've never used a TreeSet before, now's the time to look it up! The key here is to bring the same elements near one another through Sorting and then traverse to check for the repeated elements.

Final hint! You should be able to code the problem on viewing this.

One way to solve this problem is to use Array Sort.
1. Sort the array numerically, begin iterating the array.
2. Check the previous element in the array. If it equals the current element, you have a duplicate.
3. Using a TreeSet can radically simplify the implementation.

public static String duplicate(int[] numbers){
    





    
}

This Coding Interview Question is available with an answer in the following programming languages :

Java

Python

Repeated Elements in an Array

Quick hint to get things rolling

Final hint! You should be able to code the problem on viewing this.

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This Coding Interview Question is available with an answer in the following programming languages :