LeetCode-326 Power of Three

https://leetcode.com/problems/power-of-three/

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

Follow up:
Could you do it without using any loop / recursion?

1、一直整除3，直至最终为1，且无余数（136ms）

class Solution {
public:
    bool isPowerOfThree(int n) {
        if(n == 1)
            return true;
        while(n/3!=0){
            if(n%3 != 0)
                return false;
            if(n/3 == 1)
                return true;
            n /= 3;
        }
        return false;
    }
};

简洁：

class Solution {
public:
    bool isPowerOfThree(int n) {
        while(n != 0 && n%3 == 0){
            n /= 3;
        }
        if(n == 1)
            return true;
        return false;
    }
};

2、网上看到以下一种方法，技巧性，1162261467 = 3^19, 3^20 is bigger than int.  （132ms）

class Solution {

public:
    bool isPowerOfThree(int n) {
        return (n>0 && 1162261467%n == 0);
    }
};