347. Leetcode top K frequent elements

leetcode_347_top_k_frequent_element.rb

=begin

Leetcode 347. Top K Frequent Elements
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]

=end

def top_k_frequent(nums, k)
    fre ={}
    nums.each {|el| fre[el] = fre[el] ? fre[el] + 1 : 1}
    fre.sort_by{|k,v| -v }.map{|x| x[0]}[0...k]
end