Add solution #1998

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,678 LeetCode solutions in JavaScript
+# 1,679 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1533,6 +1533,7 @@
 1995|[Count Special Quadruplets](./solutions/1995-count-special-quadruplets.js)|Easy|
 1996|[The Number of Weak Characters in the Game](./solutions/1996-the-number-of-weak-characters-in-the-game.js)|Medium|
 1997|[First Day Where You Have Been in All the Rooms](./solutions/1997-first-day-where-you-have-been-in-all-the-rooms.js)|Medium|
+1998|[GCD Sort of an Array](./solutions/1998-gcd-sort-of-an-array.js)|Hard|
 2000|[Reverse Prefix of Word](./solutions/2000-reverse-prefix-of-word.js)|Easy|
 2011|[Final Value of Variable After Performing Operations](./solutions/2011-final-value-of-variable-after-performing-operations.js)|Easy|
 2016|[Maximum Difference Between Increasing Elements](./solutions/2016-maximum-difference-between-increasing-elements.js)|Easy|

solutions/1998-gcd-sort-of-an-array.js

@@ -0,0 +1,69 @@
+/**
+ * 1998. GCD Sort of an Array
+ * https://leetcode.com/problems/gcd-sort-of-an-array/
+ * Difficulty: Hard
+ *
+ * You are given an integer array nums, and you can perform the following operation any
+ * number of times on nums:
+ * - Swap the positions of two elements nums[i] and nums[j] if gcd(nums[i], nums[j]) > 1
+ *   where gcd(nums[i], nums[j]) is the greatest common divisor of nums[i] and nums[j].
+ *
+ * Return true if it is possible to sort nums in non-decreasing order using the above swap
+ * method, or false otherwise.
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var gcdSort = function(nums) {
+  const maxNum = Math.max(...nums);
+  const parent = new Array(maxNum + 1).fill().map((_, i) => i);
+  const minPrime = new Array(maxNum + 1).fill(0);
+  for (let i = 2; i <= maxNum; i++) {
+    if (minPrime[i] === 0) {
+      for (let j = i; j <= maxNum; j += i) {
+        minPrime[j] = i;
+      }
+    }
+  }
+
+  const groups = new Map();
+  for (const num of nums) {
+    let curr = num;
+    const primes = new Set();
+    while (curr > 1) {
+      const prime = minPrime[curr];
+      primes.add(prime);
+      curr /= prime;
+    }
+    for (const prime of primes) {
+      if (!groups.has(prime)) groups.set(prime, []);
+      groups.get(prime).push(num);
+    }
+  }
+
+  for (const numbers of groups.values()) {
+    for (let i = 1; i < numbers.length; i++) {
+      union(numbers[i - 1], numbers[i], parent);
+    }
+  }
+
+  const sorted = [...nums].sort((a, b) => a - b);
+  for (let i = 0; i < nums.length; i++) {
+    if (find(nums[i], parent) !== find(sorted[i], parent)) {
+      return false;
+    }
+  }
+
+  return true;
+
+  function find(x, parent) {
+    if (parent[x] !== x) parent[x] = find(parent[x], parent);
+    return parent[x];
+  }
+
+  function union(x, y, parent) {
+    parent[find(x, parent)] = find(y, parent);
+  }
+};