[LeetCode] 263. Ugly Number 丑陋数

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

写一个程序能判断一个数是不是丑陋数，丑陋数是只含有2，3，5质数因子的数。

解法：循环2，3，5，然后不停的除以这些质数，如果能整除就继续，最后剩余的数字是1的话就是丑陋数。

Java:

for (int i=2; i<6 && num>0; i++)
    while (num % i == 0)
        num /= i;
return num == 1;

Python:

class Solution:
    # @param {integer} num
    # @return {boolean}
    def isUgly(self, num):
        if num == 0:
            return False
        for i in [2, 3, 5]:
            while num % i == 0:
                num /= i
        return num == 1　　

Python:

for p in 2, 3, 5:
    while num % p == 0 < num:
        num /= p
return num == 1

C++:　　

for (int i=2; i<6 && num; i++)
    while (num % i == 0)
        num /= i;
return num == 1;　

C++:

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

C++:

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;
    }
};

　　 

类似题目：

[LeetCode] 264. Ugly Number II 丑陋数 II

[LeetCode] 313. Super Ugly Number 超级丑陋数

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