263_Ugly Number

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.

 

ugly number指的是因子最終能分解成2 3 5的數字，1也認爲是特殊的ugly number

循環相除，能被2 3 5之一整除的話，繼續循環，知道一個數字不能被2 3 5任何數字整除。此時這個數字不是1的話，則說明這個num不是ugly number，如果1的話則說明是ugly number。

 

bool isUgly(int num) {
    if(num < 1)
    {
        return 0;
    }
    while(num > 1)
    {
        if(num % 2 == 0)
        {
            num /= 2;
            continue;
        }
        else if(num % 3 == 0)
        {
            num /= 3;
            continue;
        }
        else if(num % 5 == 0)
        {
            num /= 5;
            continue;
        }
        return 0;
    }
    return 1;
}