Least Number of Unique Integers after K Removals

 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

My answer:

Basic logic: get count of each number, sort them ascending by count, reduce k by each count from the num with smallest quantity until k is negative. Reducing k by one number's count with remaining k>=0 meaning such number can be removed given k elements will be removed

class Solution {
    public int findLeastNumOfUniqueInts(int[] arr, int k) {
        Map<Integer, Integer> numCountMap = new HashMap<Integer, Integer>();
        for (int i = 0; i < arr.length; i ++) {
            Integer count = numCountMap.getOrDefault(arr[i], 0);
            count ++;
            numCountMap.put(arr[i], count);
        }
        List<Integer> list = new ArrayList<>(numCountMap.values());
        Collections.sort(list);
        int uniqNumCount= list.size();
        for (Integer element : list) {
            k -= element;
            if (k < 0) {
                break;
            } else {
                uniqNumCount --;
            }
            
        }
        return uniqNumCount;
 
    }
}