263 - Ugly Number

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最新推荐文章于 2022-11-24 23:52:31 发布

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分类专栏： leetcode 文章标签： leetcode 算法

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本文介绍了一种使用C++编程语言来判断一个给定的数字是否为丑数的方法。丑数定义为只包含2、3、5这三个质因数的正整数。文章通过具体的示例解释了如何实现这一功能，并提供了完整的代码示例。

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Problem

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.

Note:

1 is typically treated as an ugly number.
Input is within the 32-bit signed integer range: [−2³¹, 2³¹− 1].

Code

class Solution {
    public:
    long logN(long a, long b) {
        return log(b * 1.0) / log(a * 1.0);
    }
    
    long yu(long n, long m) {
        int num = logN(m, n);
        while (num) {
            int a = pow(m, num);
            while (n % a == 0) {
                n /= a;
            }
            num /= 2;
        }
        return n;
    }
    
    bool isUgly(int n) {
        long num = n;
        if (num < 0) {
            return 0;
        }
        num = yu(num, 2);
        if (num == 1) {
            return true;
        }
        num = yu(num, 3);
        if (num == 1) {
            return true;
        }
        return yu(num, 5) == 1;
    }
};