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.
solution:
如果输入为0,则不是丑数。因为第一个丑数是1
先除以2,除到余数不为0
再除以3,除到余数不为0
最后除以5,最后的余数如果为1,则为丑数
code:
class Solution {
public:
bool isUgly(int num) {
if(num==0) return false;
while(num%2==0)
num/=2;
while(num%3==0)
num/=3;
while(num%5==0)
num/=5;
return (num==1)? true:false;
}
};