Add solution #319

Author: JoshCrozier

README.md

@@ -239,6 +239,7 @@
 309|[Best Time to Buy and Sell Stock with Cooldown](./0309-best-time-to-buy-and-sell-stock-with-cooldown.js)|Medium|
 316|[Remove Duplicate Letters](./0316-remove-duplicate-letters.js)|Medium|
 318|[Maximum Product of Word Lengths](./0318-maximum-product-of-word-lengths.js)|Medium|
+319|[Bulb Switcher](./0319-bulb-switcher.js)|Medium|
 322|[Coin Change](./0322-coin-change.js)|Medium|
 326|[Power of Three](./0326-power-of-three.js)|Easy|
 328|[Odd Even Linked List](./0328-odd-even-linked-list.js)|Medium|

solutions/0319-bulb-switcher.js

@@ -0,0 +1,22 @@
+/**
+ * 319. Bulb Switcher
+ * https://leetcode.com/problems/bulb-switcher/
+ * Difficulty: Medium
+ *
+ * There are n bulbs that are initially off. You first turn on all the bulbs, then you turn
+ * off every second bulb.
+ *
+ * On the third round, you toggle every third bulb (turning on if it's off or turning off if
+ * it's on). For the ith round, you toggle every i bulb. For the nth round, you only toggle
+ * the last bulb.
+ *
+ * Return the number of bulbs that are on after n rounds.
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var bulbSwitch = function(n) {
+  return Math.floor(n ** 0.5);
+};