leetcode263. Ugly Number

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本文介绍了一个简单的算法，用于判断一个给定的正整数是否为丑数。丑数定义为只包含质因数2、3和5的正整数。文章提供了一段Java代码实现，该算法的时间复杂度为O(1)，空间复杂度也为O(1)。

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.

解法

/**
 * @Author taotao
 * @Time O(1) 
 * @Space O(1)
 */
public class Solution {
    public boolean isUgly(int num) {
        if (num < 1) {
            return false;
        }

        while (num % 2 == 0) {
            num = num / 2;
        }
        while (num % 3 == 0) {
            num = num / 3;
        }
        while (num % 5 == 0) {
            num = num / 5;
        }

        return num == 1;
    }
}