题目
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.
解题思路
- 小于1的不是丑数
- 大于1的时候，如果能被2整除，就循环除以2，直到不能被2整除；同理对3，5执行同样操作
- 等于1的话是丑数，不等于1（大于1）说明该数还有其他因子，不是丑数
代码
func isUgly(num int) bool {
if num < 1 {
return false
}
for ; num > 1 && num % 2 == 0 ; {
num /= 2
}
for ; num > 1 && num % 3 == 0 ; {
num /= 3
}
for ; num > 1 && num % 5 == 0 ; {
num /= 5
}
if num == 1 {
return true
}
return false
}
