LeetCode----326. Power of Three(Java)

 package isPowerOfThree326;
 /*
  Given an integer, write a function to determine if it is a power of three.
  */
 public class Solution {
     /*
     //题目理解错误，理解成3次开方
     public static boolean isPowerOfThree(int n) {
         if (n==1)
             return true;
         else{
             for(int i=2;i<=Math.sqrt(n);i++){
                 if(n%i==0){
                     n=n/i;
                     if(n%i==0){
                         n=n/i;
                         if (n%i==0){
                             n=n/i;
                             return isPowerOfThree(n);
                         }
                         else
                             return false;
                     }
                     return false;
                 }
             }
             return false;
         }
     }
     */
     public static boolean isPowerOfThree(int n){
         if (n==1)
             return true;
         else if (n==0)
             return false;
         else if (n%3==0){
             n=n/3;
             return isPowerOfThree(n);
         }
         else
             return false;

     }
     public static void main(String[] args) {
         // TODO Auto-generated method stub
         System.out.println(isPowerOfThree(-3));
     }

 }