215. Kth Largest Element in an Array

Author: remy727

README.md

@@ -74,6 +74,7 @@
 | 208 | Implement Trie (Prefix Tree) | [Ruby](./algorithms/ruby/0208-implement-trie-prefix-tree.rb) | Medium |
 | 210 | Course Schedule II | [Ruby](./algorithms/ruby/0210-course-schedule-ii.rb) | Medium |
 | 211 | Design Add and Search Words Data Structure | [Ruby](./algorithms/ruby/0211-design-add-and-search-words-data-structure.rb) | Medium |
+| 215 | Kth Largest Element in an Array | [Ruby](./algorithms/ruby/0215-kth-largest-element-in-an-array.rb) | Medium |
 | 226 | Invert Binary Tree | [Ruby](./algorithms/ruby/0226-invert-binary-tree.rb) | Easy |
 | 227 | Basic Calculator II | [Ruby](./algorithms/ruby/0227-basic-calculator-ii.rb) | Medium |
 | 230 | Kth Smallest Element in a BST | [Ruby](./algorithms/ruby/0230-kth-smallest-element-in-a-bst.rb) | Medium |

algorithms/ruby/0215-kth-largest-element-in-an-array.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+# 215. Kth Largest Element in an Array
+# https://leetcode.com/problems/kth-largest-element-in-an-array
+# Medium
+
+=begin
+Given an integer array nums and an integer k, return the kth largest element in the array.
+
+Note that it is the kth largest element in the sorted order, not the kth distinct element.
+
+You must solve it in O(n) time complexity.
+
+Example 1:
+Input: nums = [3,2,1,5,6,4], k = 2
+Output: 5
+
+Example 2:
+Input: nums = [3,2,3,1,2,4,5,5,6], k = 4
+Output: 4
+
+Constraints:
+1 <= k <= nums.length <= 105
+-104 <= nums[i] <= 104
+=end
+
+# @param {Integer[]} nums
+# @param {Integer} k
+# @return {Integer}
+def find_kth_largest(nums, k)
+  nums.sort[-k]
+end
+
+# ********************#
+#       TEST         #
+# ********************#
+
+require "test/unit"
+class Test_find_kth_largest < Test::Unit::TestCase
+  def test_
+    assert_equal 5, find_kth_largest([3, 2, 1, 5, 6, 4], 2)
+    assert_equal 4, find_kth_largest([3, 2, 3, 1, 2, 4, 5, 5, 6], 4)
+  end
+end
+
+# ********************#
+#     Benchmark       #
+# ********************#
+
+require "benchmark"
+
+nums = [3, 2, 3, 1, 2, 4, 5, 5, 6]
+k = 4
+Benchmark.bm do |x|
+  x.report("find_kth_largest: ") { find_kth_largest(nums, k) }
+end