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:
1
is typically treated as an ugly number.- Input is within the 32-bit signed integer range.
检测一个数是否是ugly number。
ugly number 满足以下条件:
- 正整数;
- 质因数仅含2、3、5;
- 特别地,1是ugly number。
由2可知,如果一个数是ugly number,除去这个数所有2、3、5的因数,结果为1。
代码如下:
bool isUgly(int num) { if (num <= 0) return false; if (num == 1) return true; while (num % 2 == 0) num /= 2; while (num % 3 == 0) num /= 3; while (num % 5 == 0) num /= 5; return num == 1; }