James Pan

原题网址：https://leetcode.com/problems/ugly-number/ Write a program to check whether a given number is an ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. F

原题网址：https://leetcode.com/problems/factorial-trailing-zeroes/ Given an integer n, return the number of trailing zeroes in n!. Note: Your solution should be in logarithmic time complexity. 方法：

原题网址：https://leetcode.com/problems/bulb-switcher/ 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 e