Add solution #172

Author: JoshCrozier

README.md

@@ -164,6 +164,7 @@
 168|[Excel Sheet Column Title](./0168-excel-sheet-column-title.js)|Easy|
 169|[Majority Element](./0169-majority-element.js)|Easy|
 171|[Excel Sheet Column Number](./0171-excel-sheet-column-number.js)|Easy|
+172|[Factorial Trailing Zeroes](./0172-factorial-trailing-zeroes.js)|Medium|
 173|[Binary Search Tree Iterator](./0173-binary-search-tree-iterator.js)|Medium|
 179|[Largest Number](./0179-largest-number.js)|Medium|
 187|[Repeated DNA Sequences](./0187-repeated-dna-sequences.js)|Medium|

solutions/0172-factorial-trailing-zeroes.js

@@ -0,0 +1,17 @@
+/**
+ * 172. Factorial Trailing Zeroes
+ * https://leetcode.com/problems/factorial-trailing-zeroes/
+ * Difficulty: Medium
+ *
+ * Given an integer n, return the number of trailing zeroes in n!.
+ *
+ * Note that n! = n * (n - 1) * (n - 2) * ... * 3 * 2 * 1.
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var trailingZeroes = function(n) {
+  return n < 5 ? 0 : Math.floor(n / 5) + trailingZeroes(n / 5);
+};