Added Kth Largest Element in an Array

Author: ignacio-chiazzo

LeetcodeProblems/Implement_stack_using_queues.js

@@ -24,8 +24,6 @@ Depending on your language, queue may not be supported natively. You may simulat
 You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).
 */
 
-
-
 class MyStack  {
   constructor() {
     this.q1 = [];
@@ -95,4 +93,4 @@ var myStack = new MyStack();
   console.log(myStack.pop());
 }
 
-module.exports.main = main;
+module.exports.main = main;

LeetcodeProblems/Kth_Largest_Element_in_an_Array.js

@@ -0,0 +1,66 @@
+/*
+Kth Largest Element in an Array
+https://leetcode.com/problems/kth-largest-element-in-an-array/description/
+
+Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.
+
+Example 1:
+
+Input: [3,2,1,5,6,4] and k = 2
+Output: 5
+Example 2:
+
+Input: [3,2,3,1,2,4,5,5,6] and k = 4
+Output: 4
+Note: 
+You may assume k is always valid, 1 ≤ k ≤ array's length.
+*/
+
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ */
+var findKthLargest = function(nums, k) {
+  for(var i = Math.floor(nums.length/2) - 1; i >= 0; i--) {
+    heapify(nums, nums.length, i);
+  }
+  
+  for(var i = nums.length -1; i >= nums.length - k - 1 && i >= 0; i--) {
+    swap(nums, 0, i);
+    heapify(nums, i, 0);
+  }
+  
+  return nums[nums.length - k];
+}
+
+var heapify = function(nums, length, i) {
+  var left = 2 * i + 1;
+  var right = 2 * i + 2;
+  
+  if(left >= length)
+    return;
+  
+  if(nums[i] < nums[left] && (right >= length || nums[left] > nums[right])) { 
+    swap(nums, left, i);
+    heapify(nums, length, left);
+  } else if(right < length && nums[right] > nums[i]) {
+    swap(nums, right, i)
+    heapify(nums, length, right)
+  }
+}
+
+var swap = function(nums, a, b) {
+  const temp = nums[a];
+  nums[a] = nums[b];
+  nums[b] = temp;
+}
+
+var main = function(nums) {
+  console.log(findKthLargest([3,2,1,5,6,4], 2));
+  console.log(findKthLargest([3,2,3,1,2,4,5,5,6], 4));
+  console.log(findKthLargest([0], 1));
+  console.log(findKthLargest([], 1));
+}
+
+module.exports.main = main;

LeetcodeProblems/Sum_Of_Square_Numbers.js

@@ -14,7 +14,6 @@ Input: 3
 Output: False
 */
 
-
 /**
  * @param {number} c
  * @return {boolean}
@@ -42,3 +41,5 @@ var main = function() {
   console.log(judgeSquareSum(24));
   console.log(judgeSquareSum(25));
 }
+
+module.exports.main = main;