Given an integer, write a function to determine if it is a power of three.

Example 1:

Input: 27Output: true

Example 2:

Input: 0Output: false

Example 3:

Input: 9Output: true

Example 4:

Input: 45Output: false

Follow up:

public static List
    
      list = null;    static{        list = new ArrayList<>();        for(int i= 0;i
     
       (long)Integer.MAX_VALUE){                  break;            }            list.add(value.longValue());        }    }    //发现先把数据取出来 比对一下 妥妥的  但是用了loop 哎    public static boolean isPowerOfThree(int n) {           return list.contains((long)n);    }    //看看大神的表演 原来这样就可以啦    public static boolean isPowerOfThree2(int n) {        // 1162261467 is 3^19,  3^20 is bigger than int        return ( n>0 &&  1162261467%n==0);    }    //好吧 都用上公式啦    public static boolean isPowerOfThree3(int n) {        return (Math.log10(n) / Math.log10(3)) % 1 == 0;    }    public static void main(String[] args) {        System.out.println(isPowerOfThree3(9));        System.out.println(isPowerOfThree3(27));        System.out.println(isPowerOfThree3(0));        System.out.println(isPowerOfThree3(45));             //这里会是什么//          Integer a = 6;//          Long b = 6L;//          System.out.println(a.equals(b));    }
     
    

git：https://github.com/woshiyexinjie/leetcode-xin