Given an array arr of integers, find all the elements that occur more than once in the array. If no element repeats, return an empty array.
Examples:
Input: arr[] = [2, 3, 1, 2, 3]
Output: [2, 3]
Explanation: 2 and 3 occur more than once in the given array.
Input: arr[] = [0, 3, 1, 2]
Output: []
Explanation: There is no repeating element in the array, so the output is empty.
Input: arr[] = [2]
Output: []
Explanation: There is single element in the array. Therefore output is empty.
Constraints:
1 <= arr.size() <= 106
0 <= arr[i] <= 106
