1481\. Least Number of Unique Integers after K Removals

Medium

Given an array of integers `arr` and an integer `k`. Find the _least number of unique integers_ after removing **exactly** `k` elements**.**

**Example 1:**

**Input:** arr = [5,5,4], k = 1

**Output:** 1

**Explanation:** Remove the single 4, only 5 is left.

**Example 2:**

**Input:** arr = [4,3,1,1,3,3,2], k = 3

**Output:** 2

**Explanation:** Remove 4, 2 and either one of the two 1s or three 3s. 1 and 3 will be left.

**Constraints:**

*   `1 <= arr.length <= 10^5`
*   `1 <= arr[i] <= 10^9`
*   `0 <= k <= arr.length`