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.
Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.
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class Solution { public: bool isUgly(int num) { if(num > 1) { while(num % 2 == 0) num /= 2; while(num % 3 == 0) num /= 3; while(num % 5 == 0) num /= 5; } return num == 1; } };
另一种写法：
class Solution { public: bool isUgly(int num) { while(num > 1) { if(num % 2 == 0) num /= 2; else if(num % 3 == 0) num /= 3; else if(num % 5 == 0) num /= 5; else break; } return num == 1; } };
第一种写法效率更高。
原文：http://www.cnblogs.com/aprilcheny/p/4946870.html