LeetCode - 263 Ugly Number

作者 QIFAN 日期 2016-07-14
LeetCode - 263 Ugly Number

Difficulty:Easy

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.

思路

如果这个数只有2,3,5这三个质数约数,则为ugly number。换句话说,ugly number一定是且只能是2,3,5这三个数自由组合的乘积。

别忘了1是特殊情况

代码

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

原题链接:https://leetcode.com/problems/ugly-number/