[LeetCode從零單刷]Ugly Number

[LeetCode從零單刷]Ugly Number

題目：

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.

解答：

如果某個數是丑數，那麼它一定可以不斷被 2 或者 3 或者 5 整除，然後除以之後的結果依然滿足丑數的條件。

不斷循環，直到這個數不再變化。此時如果是 1 則是丑數，否則不是。

class Solution {
public:
    bool isUgly(int num) {
        if(num == 1 || num == 2 || num == 3 || num == 5)    return true;
        
        int tmp = 0;
        while(tmp != num)
        {
            tmp = num;
            if(num % 2 == 0)    num = num / 2;
            if(num % 3 == 0)    num = num / 3;
            if(num % 5 == 0)    num = num / 5;
        }
        
        if(tmp == 1)
            return true;
        else
            return false;
    }
};