LeetCode--No.263--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.

public class Solution {
public boolean isUgly(int num) {
if (num <=0)
return false;
while(num % 2 == 0)
num = num/2;
while(num % 3 == 0)
num = num/3;
while(num % 5 == 0)
num = num/5;
return num == 1;
}
}

这样写会超时。因为会进行很多不必要的判断条件。

public class Solution {
public boolean isUgly(int num) {
if (num <=0)
return false;
if (num<=5)
return true;
while(num >=5){
if(num % 2 == 0)
num /= 2;
if(num % 3 == 0)
num /= 3;
if(num % 5 == 0)
num /= 5;
}
if(num < 5)
return true;
else
return false;
}
}