I was given a task to write a program which searches through an array and returns the first element that is duplicated. we are talking about a dynamic array (scanning size from the user) and the array itself is not sorted, and the values inside are from 0-3n (n is the size of the array) I thought about sorting it, but I need the first element from the original array, and I am not sure I can get it if I sort the array before checking it.. I thought about doing it with two loops, but I need it with time complexity of O(n) and I'm kinda stuck. Any ideas?
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