Add solution #858

Author: JoshCrozier

README.md

@@ -665,6 +665,7 @@
 855|[Exam Room](./0855-exam-room.js)|Medium|
 856|[Score of Parentheses](./0856-score-of-parentheses.js)|Medium|
 857|[Minimum Cost to Hire K Workers](./0857-minimum-cost-to-hire-k-workers.js)|Hard|
+858|[Mirror Reflection](./0858-mirror-reflection.js)|Medium|
 867|[Transpose Matrix](./0867-transpose-matrix.js)|Easy|
 868|[Binary Gap](./0868-binary-gap.js)|Easy|
 872|[Leaf-Similar Trees](./0872-leaf-similar-trees.js)|Easy|

solutions/0858-mirror-reflection.js

@@ -0,0 +1,33 @@
+/**
+ * 858. Mirror Reflection
+ * https://leetcode.com/problems/mirror-reflection/
+ * Difficulty: Medium
+ *
+ * There is a special square room with mirrors on each of the four walls. Except for the southwest
+ * corner, there are receptors on each of the remaining corners, numbered 0, 1, and 2.
+ *
+ * The square room has walls of length p and a laser ray from the southwest corner first meets the
+ * east wall at a distance q from the 0th receptor.
+ *
+ * Given the two integers p and q, return the number of the receptor that the ray meets first.
+ *
+ * The test cases are guaranteed so that the ray will meet a receptor eventually.
+ */
+
+/**
+ * @param {number} p
+ * @param {number} q
+ * @return {number}
+ */
+var mirrorReflection = function(p, q) {
+  const gcd = findGCD(p, q);
+  const m = q / gcd;
+  const n = p / gcd;
+
+  if (m % 2 === 0) return 0;
+  return n % 2 === 1 ? 1 : 2;
+};
+
+function findGCD(a, b) {
+  return b === 0 ? a : findGCD(b, a % b);
+}