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:

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

Solution

# @param {Integer[]} nums
# @param {Integer} k
# @return {Integer[]}
def top_k_frequent(nums, k)
  numhash = Hash.new(0)
  nums.each {|num| numhash[num] += 1}
  newhash = numhash.sort_by {|k, v| -v}
  ret_array = []
  for i in 0...k
    ret_array << newhash[i][0]
  end
  return ret_array
end