[LintCode] 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. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.

Notice

Note that 1 is typically treated as an ugly number.

Example
Given num = 8 return true
Given num = 14 return false

 

LeetCode上的原题，请参见我之前的博客Ugly Number。

 

解法一：

class Solution {
public:
    /**
     * @param num an integer
     * @return true if num is an ugly number or false
     */
    bool isUgly(int num) {
        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 num == 1;
    }
};

 

解法二：

class Solution {
public:
    /**
     * @param num an integer
     * @return true if num is an ugly number or false
     */
    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;
    }
};