Time Complexity: O(N log N), where N is the size of the array. This is because we are sorting the array, which takes O(N log N) time.

Space Complexity: O(1), as we are sorting the array in-place and not using any additional data structures that grow with input size.

Better Approach

Algorithm

Create a frequency array of size N+1 and initialize all elements to 0. This will keep track of the occurrences of each element in the array.
Traverse through the given array.
For each element, check its frequency in the frequency array:

If the frequency is 0, increase it by 1, indicating that the element has been encountered for the first time.
If the frequency is not 0, this means the element has appeared before, and it is the required answer.

Return or print the element as the first repeating element.

Code

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