LeetCode:Ugly Number

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. 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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Solution:

 1 class Solution {
 2 public:
 3     bool isUgly(int num) {
 4         if(num<1) return false;
 5         if(num==1) return true;
 6         
 7         if(num%2==0) 
 8              return isUgly(num/2);
 9         else if(num%3==0) 
10              return isUgly(num/3);
11         else if(num%5==0) 
12             return isUgly(num/5);
13             
14         return false;
15         
16     }
17 };

 

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;
        
        if(num==1) return true;
        else return false;
        
        
    }
};

 

posted @ 2016-01-18 21:17  尾巴草  阅读(283)  评论(0)  编辑  收藏  举报