1481. Least Number of Unique Integers after K Removals

Problem

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&nbsp;<= 10^5

• 1 <= arr[i] <= 10^9

• 0 <= k&nbsp;<= arr.length

Solution (Java)

class Solution {
    public int findLeastNumOfUniqueInts(int[] arr, int k) {
        Map<Integer, Integer> count = new HashMap<>();
        for (int a : arr) {
            count.put(a, 1 + count.getOrDefault(a, 0));
        }
        int remaining = count.size();
        int occur = 1;
        int[] occurrenceCount = new int[arr.length + 1];

        for (int v : count.values()) {
            ++occurrenceCount[v];
        }
        while (k > 0) {
            if (k - occur * occurrenceCount[occur] >= 0) {
                k -= occur * occurrenceCount[occur];
                remaining -= occurrenceCount[occur++];
            } else {
                return remaining - k / occur;
            }
        }
        return remaining;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).