[Leetcode-263] Ugly Number（丑陋数）

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.

【分析】思路：根据丑陋数的定义，我们将给定数除以2、3、5，直到无法整除，也就是除以2、3、5的余数不再为0时停止。这时如果得到1，说明是所有因子都是2或3或5，如果不是1，则不是丑陋数。

bool isUgly(int num) {

    if(num<=0)
        return 0;

    int rem2 = num % 2;
    int rem3 = num % 3;
    int rem5 = num % 5;

    while(rem2 == 0 || rem3 == 0 || rem5 == 0) {
        if(rem2 == 0) {
            num = num / 2;
        } else if(rem3 == 0) {
            num = num / 3;
        } else {
            num = num / 5;
        }
        rem2 = num % 2;
        rem3 = num % 3;
        rem5 = num % 5;
    }
    return num == 1;
}