add: 只出现一次的数字等

src/math/factorial-trailing-zeroes.js

@@ -0,0 +1,10 @@
+// LeetCode 172. 阶乘后的零 https://leetcode-cn.com/problems/factorial-trailing-zeroes/submissions/
+// LintCode 2. 尾部的零 https://www.lintcode.com/problem/trailing-zeros/description
+
+export default (n) => {
+  let sum = 0
+  while (n !== 0) {
+    sum += Math.floor(n /= 5)
+  }
+  return sum
+}