leetcode 263. Ugly Number 丑数

桃扇骨 2022-06-08 13:24 186阅读 0赞

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.

就是判断一个数据是不是丑数，直接做除法即可。

建议和[leetcode 264. Ugly Number II 计算第K个丑数][leetcode 264. Ugly Number II _K] 和 [leetcode 313. Super Ugly Number 超级丑数][leetcode 313. Super Ugly Number] 一起学习

代码如下：

/*
     * 不要直接求所有的质数，然后寻找素数，最后作判断，太麻烦了
     * 直接循环除法即可
     * */
    class Solution
    {
        public boolean isUgly(int num) 
        {
            if(num<=0)
                return false;
            if(num==1)
                return true;    
            while(num>=2 && num%2==0)
                num=num/2;
            while(num>=3 && num%3==0)
                num=num/3;
            while(num>=5 && num%5==0)
                num=num/5;
            return num==1? true :false;
        }
    }

下面是C++的做法，不要直接寻找所有的质数，直接在原先的数据上做处理即可，代码如下：

#include <iostream>
    #include <vector>
    #include <map>
    #include <set>
    #include <queue>
    #include <stack>
    #include <string>
    
    using namespace std;
    
    class Solution 
    {
    public:
        bool isUgly(int num) 
        {
            if (num <= 0)
                return false;
            else if (num == 1)
                return true;
    
            while (num > 1 && num % 2 == 0)
                num /= 2;
            while (num > 1 && num % 3 == 0)
                num /= 3;
            while (num > 1 && num % 5 == 0)
                num /= 5;
    
            return num == 1 ? true : false;
        }
    };

[leetcode 264. Ugly Number II _K]: http://blog.csdn.net/jackzhang_123/article/details/78109430
[leetcode 313. Super Ugly Number]: http://blog.csdn.net/jackzhang_123/article/details/78150024