LeetCode 题解（187): Ugly Number

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本文介绍了一种用于判断一个给定整数是否为丑数的算法。丑数定义为只包含质因数2、3和5的正整数。文章提供了C++、Java和Python三种语言的具体实现。

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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. 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.

题解：

满足Ugly number的条件是 num /= pow(2, max) /= pow(3, max) /= pow(5, max) == 1。

C++版：

class Solution {
public:
    bool isUgly(int num) {
        if(num == 0)
            return false;
        while(num % 2 == 0)
            num /= 2;
        while(num % 3 == 0)
            num /= 3;
        while(num % 5 == 0)
            num /= 5;
        return num == 1? true : false;
    }
};

Java版：

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

Python版：

class Solution(object):
    def isUgly(self, num):
        """
        :type num: int
        :rtype: bool
        """
        if num == 0:
            return False

        while num % 2 == 0:
            num /= 2

        while num % 3 == 0:
            num /= 3
   
        while num % 5 == 0:
            num /= 5
  
        if num == 1:
            return True
        else:
            return False