Challenge: Find Duplicates in Array
Write a function to find the duplicates in an array in the most efficient way.
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Problem statement
Given an array, find all the duplicates that exist in that array.
Input
An integer array.
Output
The output is an ArrayList containing the duplicates if they exist and an empty ArrayList if they don’t.
Sample input
int arr[] = {1, 3, 4, 3, 5, 4, 100, 100};
Sample output
ArrayList <Integer> output = {3, 4, 100};
Coding exercise
Take a close look and design a step-by-step algorithm before jumping to the implementation. This problem is designed for your practice, so try to solve it on your own first. If you get stuck, you can always refer to the solution provided in the code tab. Good Luck!
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