Smallest Subarray Covering All Values

You are given an array of integers. Your task is to find the smallest contiguous subarray that contains every distinct integer that appears in the original array.

Problem Details

• Input: An array of integers (the array can be unsorted, and integers may repeat).
• Output: A contiguous subarray (i.e., a slice of the original array) that is the shortest in length and contains every distinct integer from the input array at least once. If there are multiple subarrays of the smallest length satisfying the condition, you may return any one of them.

Requirements

• Correctness: The returned subarray must include every unique number present in the input array.
• Optimality: Strive for an efficient algorithm (ideally, better than O(n²) if possible) in terms of time complexity.
• Edge Cases: Consider cases such as an empty array or an array with a single element.

Example

Suppose the input array is: [1, 2, 2, 3, 1, 2, 3]

• The distinct numbers in the array are: 1, 2, 3.
• One possible correct answer is [2, 3, 1] because this subarray (starting at index 2 and ending at index 4) contains all the distinct integers. Other equally valid answers might exist.

Construct your solution as a function or method in a programming language of your choice.