Longest Subarray with at most K Distinct Integers in Rust

Given an array of integers, find the longest subarray that contains at most K distinct integers and return its length.

Example

Input: nums = [1, 2, 1, 2, 3], k = 2
Output: 4
Explanation:the subarray nums[0...3] contains 2 distinct values: [1, 2] and is the longest subarray

Your algorithm should run in O(n^2) time and use O(n) extra space.