Magical String

Author: lessfish

Algorithms/Magical String/magical-string.js

@@ -0,0 +1,25 @@
+// Source : https://leetcode.com/problems/magical-string/
+// Author : Han Zichi
+// Date   : 2017-01-10
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var magicalString = function(n) {
+  let arr = [1, 2, 2];
+  let index = 2;
+
+  while (arr.length < n) {
+    let item = arr[arr.length - 1] === 2 ? 1 : 2;
+    for (let i = 0; i < arr[index]; i++)
+      arr[arr.length] = item;
+    index++;
+  }
+
+  let ans = 0;
+  for (let i = 0; i < n; i++)
+    (arr[i] === 1) && ans++;
+
+  return ans;
+};