算法系列——Ugly Number

题目描述

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.

解题思路

题目给了一个新的概念，丑数，因式分解，只包含2，3，5这三个数。

思路也比较简单，如果能够被2整除，就不断除以2，能够被3整除，就不断除以3，能够被5整除，就不断除以5，判断最终结果是不是等于1即可。特别的，1是第一个丑数。

程序实现

class Solution {    public boolean isUgly(int num) {        if(num==0)            return false;        while(num%2==0)            num/=2;        while(num%3==0)            num/=3;        while(num%5==0)            num/=5;        return num==1;    }}