LeetCode 263 Ugly Number

Problem:

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. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.

Note that 1 is typically treated as an ugly number.

Summary:

判断一个数是不是ugly number，即质因子只有2、3、5的数。

Analysis:

判断方法即为不断除以2、3、5，看最终能否得到1。以下两种方法大同小异。

 class Solution {
 public:
     bool isUgly(int num) {
         if (num <= ) return false;

         while (num != ) {
             if (num %  == ) num /=;
             else if (num %  == ) num /=;
             else if (num %  == ) num /= ;
             else return false;
         }

         return true;
     }
 };

 class Solution {
 public:
     bool isUgly(int num) {
         if (num <= ) return false;

         while (num >=  && num %  == ) num /= ;
         while (num >=  && num %  == ) num /= ;
         while (num >=  && num %  == ) num /= ;

         return num == ;
     }
 };