Add solution #401

Author: JoshCrozier

README.md

@@ -319,6 +319,7 @@
 398|[Random Pick Index](./0398-random-pick-index.js)|Medium|
 399|[Evaluate Division](./0399-evaluate-division.js)|Medium|
 400|[Nth Digit](./0400-nth-digit.js)|Medium|
+401|[Binary Watch](./0401-binary-watch.js)|Easy|
 404|[Sum of Left Leaves](./0404-sum-of-left-leaves.js)|Easy|
 405|[Convert a Number to Hexadecimal](./0405-convert-a-number-to-hexadecimal.js)|Easy|
 407|[Trapping Rain Water II](./0407-trapping-rain-water-ii.js)|Hard|

solutions/0401-binary-watch.js

@@ -0,0 +1,35 @@
+/**
+ * 401. Binary Watch
+ * https://leetcode.com/problems/binary-watch/
+ * Difficulty: Easy
+ *
+ * A binary watch has 4 LEDs on the top to represent the hours (0-11), and 6 LEDs on the bottom
+ * to represent the minutes (0-59). Each LED represents a zero or one, with the least significant
+ * bit on the right.
+ * - For example, the below binary watch reads "4:51".
+ * Given an integer turnedOn which represents the number of LEDs that are currently on (ignoring
+ * the PM), return all possible times the watch could represent. You may return the answer in
+ * any order.
+ * The hour must not contain a leading zero.
+ * - For example, "01:00" is not valid. It should be "1:00".
+ * The minute must consist of two digits and may contain a leading zero.
+ * - For example, "10:2" is not valid. It should be "10:02".
+ */
+
+/**
+ * @param {number} turnedOn
+ * @return {string[]}
+ */
+var readBinaryWatch = function(turnedOn) {
+  const result = [];
+
+  for (let h = 0; h < 12; h++) {
+    for (let m = 0; m < 60; m++) {
+      if (h.toString(2).split('1').length - 1 + m.toString(2).split('1').length - 1 === turnedOn) {
+        result.push(`${h}:${m < 10 ? '0' + m : m}`);
+      }
+    }
+  }
+
+  return result;
+};