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:Math
思路: 如果能整除一直除2,3,5,看最后是否等于1
Time Complexity: O(N) Space Complexity: O(1)
Solution Code:
class Solution {
public boolean isUgly(int num) {
if(num < 1) return false;
int factors[] = new int[]{2, 3, 5};
for(int f: factors) {
while(num % f == 0) {
num /= f;
}
}
return num == 1;
}
}