Wiggle Sort II

Author: jeantimex

README.md

@@ -57,6 +57,7 @@ A collection of JavaScript problems and solutions for studying algorithms.
 - [Next Permutation](src/array/next-permutation.js)
 - [Find Peak Element](src/array/find-peak-element.js)
 - [Wiggle Sort](src/array/wiggle-sort.js)
+- [Wiggle Sort II](src/array/wiggle-sort-ii.js)
 - [Valid Triangle Number](src/array/valid-triangle-number.js)
 - [Find Anagram Mappings](src/array/find-anagram-mappings.js)
 - [K Empty Slots](src/array/k-empty-slots.js)

src/array/wiggle-sort-ii.js

@@ -0,0 +1,36 @@
+/**
+ * Wiggle Sort II
+ *
+ * Given an unsorted array nums, reorder it such that nums[0] < nums[1] > nums[2] < nums[3]....
+ *
+ * Example 1:
+ *
+ * Input: nums = [1, 5, 1, 1, 6, 4]
+ * Output: One possible answer is [1, 4, 1, 5, 1, 6].
+ *
+ * Example 2:
+ *
+ * Input: nums = [1, 3, 2, 2, 3, 1]
+ * Output: One possible answer is [2, 3, 1, 3, 1, 2].
+ *
+ * Note:
+ * You may assume all input has valid answer.
+ *
+ * Follow Up:
+ * Can you do it in O(n) time and/or in-place with O(1) extra space?
+ */
+
+/**
+ * O(nlogn) Solution
+ *
+ * @param {number[]} nums
+ * @return {void} Do not return anything, modify nums in-place instead.
+ */
+var wiggleSort = function(nums) {
+  const n = nums.length;
+  const sorted = nums.slice().sort((a, b) => a - b);
+
+  for (let i = 0, j = n, k = Math.floor((n + 1) / 2); i < n; i++) {
+    nums[i] = i % 2 === 0 ? sorted[--k] : sorted[--j];
+  }
+};

src/array/wiggle-sort.js

@@ -12,16 +12,8 @@
  */
 const wiggleSort = nums => {
   for (let i = 1; i < nums.length; i++) {
-    if (i % 2 !== 0 && nums[i] < nums[i - 1]) {
-      swap(nums, i, i - 1);
-    } else if (i % 2 === 0 && nums[i] > nums[i - 1]) {
-      swap(nums, i, i - 1);
+    if ((i % 2 === 0) === nums[i] > nums[i - 1]) {
+      [nums[i], nums[i - 1]] = [nums[i - 1], nums[i]];
     }
   }
 };
-
-const swap = (nums, i, j) => {
-  const tmp = nums[i];
-  nums[i] = nums[j];
-  nums[j] = tmp;
-};