263 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. 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.

最直接的办法就是不停的除以这些质数，如果剩余的数字是1的话就是Ugly number了

Java code:

 1 public boolean isUgly(int num) {
 2         if(num <=0) { return false; }
 3         while(num %2 == 0) {
 4             num /= 2;
 5         }
 6         while(num %3 == 0) {
 7             num /= 3;
 8         }
 9         while(num %5 == 0) {
10             num /= 5;
11         }
12         return num == 1;
13     }

Reference:

http://www.cnblogs.com/grandyang/p/4741934.html

263 Ugly Number

原文：http://www.cnblogs.com/anne-vista/p/4790560.html