leetcode 263. Ugly Number

题目内容

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.

题目分析

判断一个数，它的质因数是不是只有2,3,5，如果是，这个数是一个“丑数”，包含其他质因数，则不是。

所以要对给定的数不断的除2,3,5,直到除的有余数为止，如果除尽则是，否则，不是。、

public class Solution {
public boolean isUgly(int num) {
if(num<1) return false;
if(num==1) return true;

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

return num==1;

}
}