Question:

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.

 

Analysis:

问题描述：写出一个程序判断一个数字是否为ugly number。ugly number是指仅包含2，3，5因子的数，例如8是丑数，而14就不是丑数，因为它还含有因子7. 1认为是丑数。

思路：当这个数可以被2/3/5整数就一直整出，知道最后，如果剩下的是1，说明该数是丑数；若不是1，则说明该数不是丑数。

 

Answer：

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