Add solution #526

Author: JoshCrozier

README.md

@@ -422,6 +422,7 @@
 523|[Continuous Subarray Sum](./0523-continuous-subarray-sum.js)|Medium|
 524|[Longest Word in Dictionary through Deleting](./0524-longest-word-in-dictionary-through-deleting.js)|Medium|
 525|[Contiguous Array](./0525-contiguous-array.js)|Medium|
+526|[Beautiful Arrangement](./0526-beautiful-arrangement.js)|Medium|
 530|[Minimum Absolute Difference in BST](./0530-minimum-absolute-difference-in-bst.js)|Easy|
 541|[Reverse String II](./0541-reverse-string-ii.js)|Easy|
 542|[01 Matrix](./0542-01-matrix.js)|Medium|

solutions/0526-beautiful-arrangement.js

@@ -0,0 +1,35 @@
+/**
+ * 526. Beautiful Arrangement
+ * https://leetcode.com/problems/beautiful-arrangement/
+ * Difficulty: Medium
+ *
+ * Suppose you have n integers labeled 1 through n. A permutation of those n integers perm
+ * (1-indexed) is considered a beautiful arrangement if for every i (1 <= i <= n), either
+ * of the following is true:
+ * - perm[i] is divisible by i.
+ * - i is divisible by perm[i].
+ *
+ * Given an integer n, return the number of the beautiful arrangements that you can construct.
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var countArrangement = function(n) {
+  let count = 0;
+  backtrack(1, 0);
+  return count;
+
+  function backtrack(offset, used) {
+    if (offset > n) {
+      count++;
+      return;
+    }
+    for (let i = 1; i <= n; i++) {
+      if (!(used & (1 << i)) && (i % offset === 0 || offset % i === 0)) {
+        backtrack(offset + 1, used | (1 << i));
+      }
+    }
+  }
+};