263. Ugly Number

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.

Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

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思路

判断数能否被2,3,5整除，不能返回false，能的话做除法再递归，直到值为1为止

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代码

class Solution {public:    bool canBeUglyNum(int &num)    {        int numFlag[3] = {2,3,5};        for(int i=0;i<sizeof(numFlag)/sizeof(int);i++)        {            if(num % numFlag[i] == 0)            {                num /= numFlag[i];                return true;            }        }        return false;    }    bool isUgly(int num) {        if(num < 1)        {            return false;        }        while(num > 1)        {            if(!canBeUglyNum(num))            {                return false;            }        }        return true;    }};