[leetcode]263.Ugly Number

题目

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.

Example 1:

Input: 6
Output: true
Explanation: 6 = 2 × 3
Example 2:

Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2
Example 3:

Input: 14
Output: false
Explanation: 14 is not ugly since it includes another prime factor 7.

解法

思路

直接一直除以这几个数就好。如果对这几个数取余都不能得0，直接返回false。

代码

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