Smallest Subarray with K Unique Elements

Given an array of n integers, the task is to find the length of the smallest contiguous subarray that contains at least k unique elements. If no such subarray exists, output -1.

A subarray is defined as a contiguous segment of the array. Formally, if S is a subarray of A, then the uniqueness of S is given by $$\text{Unique}(S)=\left|\{x\, :\, x\in S\}\right|.$$ Your goal is to determine the minimum length L such that there exists a subarray S with length L and $$\text{Unique}(S)\ge k.$$

If no subarray satisfies the condition, output -1.

inputFormat

The first line contains two integers n and k separated by a space.

The second line contains n integers representing the array elements, separated by spaces.

Input is given via standard input (stdin).

outputFormat

Output a single integer which is the length of the smallest subarray that contains at least k unique elements, or -1 if no such subarray exists.

Output should be written to standard output (stdout).

7 3
1 2 1 2 3 2 3

3