LeetCode-in-All

347. Top K Frequent Elements

Medium

Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order.

Example 1:

Input: nums = [1,1,1,2,2,3], k = 2

Output: [1,2]

Example 2:

Input: nums = [1], k = 1

Output: [1]

Constraints:

• 1 <= nums.length <= 105
• -104 <= nums[i] <= 104
• k is in the range [1, the number of unique elements in the array].
• It is guaranteed that the answer is unique.

Follow up: Your algorithm’s time complexity must be better than O(n log n), where n is the array’s size.

Solution

defmodule Solution do
  @spec top_k_frequent(nums :: [integer], k :: integer) :: [integer]
  def top_k_frequent(nums, k) do
    nums 
    |> Enum.frequencies() 
    |> Enum.sort(fn {_, x}, {_, y} -> x > y end) 
    |> Enum.take(k)
    |> Enum.map(fn {n, _} -> n end)
  end
end

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