[LeetCode]: 263: Ugly Number

题目：

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.

分析：

说实话，题目根本没有看懂。"prime factors" 这个理解错了。正确的理解是：所有因子都是2或3或5，即这个数是由多个2,3,5相乘组成的

代码：

public boolean isUgly(int num) {

if(num<=0) return false;
if(num==1) return true;

while(num>=2 && num%2==0) num/=2;
while(num>=3 && num%3==0) num/=3;
while(num>=5 && num%5==0) num/=5;

return num==1;
}