263. 丑陋数 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.

丑陋数就是其质数因子只能是2,3,5。那么最直接的办法就是不停的除以这些质数，如果剩余的数字是1的话就是丑陋数

static public bool IsUgly(int num) {
	while (num >= 2) {
		if (num % 2 == 0) num /= 2;
		else if (num % 3 == 0) num /= 3;
		else if (num % 5 == 0) num /= 5;
		else return false;
	}
	return num == 1;
}

263. 丑陋数 Ugly Number

原文：http://www.cnblogs.com/xiejunzhao/p/abd312dbe1279df561e7187a892a4bc7.html