LeetCode 答案(Easy)（201-300）

263- Ugly Number（丑数）

Write a program to check whether a given number is an ugly number.
写一个程序来判断一个给定的数是不是“丑数”

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.
丑数是指质因数只在2，3，5中取得。例如：6和8是丑数。然而14不是，因为它有一个质因数7

Note that 1 is typically treated as an ugly number.
特别的，1 被视为丑数。

• 答案

public class Solution {
    public boolean isUgly(int num) {
        if (num <= 0)
            return false;
        if (num == 1)
            return true;
        //先让2除，除到不能除为止
        while (num >= 2 && num % 2 == 0) {
            num /= 2;
        }
         //让3除，除到不能除为止
        while (num >= 3 && num % 3 == 0) {
            num /= 3;
        }
         //让5除，除到不能除为止
        while (num >= 5 && num % 5 == 0) {
            num /= 5;
        }
        //判断最终的商是不是1
        return num == 1;

    }
}