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.

Code:

class Solution {
    public boolean isUgly(int num) {
        for (int i = 2; i < 6 && num > 0; i++) {
            while (num % i == 0)
                num /= i;
        }
        return num == 1;
    }
}

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解题思路：

• 循环查看数字是否能被2、3、4和5整除，如果整除就将数赋值为商；
• 检查循环结束，数是否等于1.