Least Number of Unique Integers after K

Tested Python solution for LeetCode 1481 with 18 pytest cases. Generate a practice environment with lcpy.

LeetCode 1481, Medium. Topics: Array, Hash Table, Greedy, Sorting, Counting. View on LeetCode.

Generate this problem as a practice environment: tested reference solution, 18 parametrized pytest cases, and a playground notebook:

lcpy gen -n 1481   # by problem number
lcpy gen -s least_number_of_unique_integers_after_k_removals   # by problem name

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Problem

Given an array of integers arr and an integer k. Find the least number of unique integers after removing exactly k elements.

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Examples

Input: arr = [5,5,4], k = 1
Output: 1
Explanation: Remove the single 4, only 5 is left.

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.

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Constraints

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

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Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

from collections import Counter


class Solution:
    # Time: O(n log n)
    # Space: O(n)
    def find_least_num_of_unique_ints(self, arr: list[int], k: int) -> int:
        counts = sorted(Counter(arr).values())
        remaining = len(counts)
        for count in counts:
            if k < count:
                break
            k -= count
            remaining -= 1
        return remaining

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Complexity

Time	Space
O(n log n)	O(n)

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Tags

NeetCode All.