leetcode-263-Ugly-Number

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描述

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.

分析

判断一个数是不是只由2、3、5相乘得到。

解决方案1(C++)

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class Solution {
public:
    bool isUgly(int num) {
        if(num <= 0) {
            return false;
        }
        for(int i=2; i <= 5; i++) {
            while(num%i == 0){
                num /= i;
            }
        }
        if(num != 1){
            return false;
        }
        return true;
    }
};

解决方案2(C)

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bool isUgly(int num) {
    if(num<=0) return false;
    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 true;
}

解决方案2(Python)

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class Solution(object):
    def isUgly(self, num):
        """
        :type num: int
        :rtype: bool
        """
        if num < 0:
            return False
        while num % 2 == 0 and num != 0:
            num /= 2
        while num % 3 == 0 and num != 0:
            num /= 3
        while num % 5 == 0 and num != 0:
            num /= 5
        if num != 1:
            return False
        return True

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