leetcode 326. Powers of 3

Given an integer, write a function to determine if it is a power of 3.Returns true if so; otherwise, returns false .

An integer n is a power of 3 if there is an integer x such that n == 3^x

Example 1:

Input: n = 27
Output: true
Example 2:

Input: n = 0
Output: false
Example 3:

Input: n = 9
Output: true
Example 4:

Input: n = 45
Output: false

Tip:

-2³¹<= n <= 2³¹ - 1

Thinking:

The power of 3 must be greater than 0, and the remainder after dividing the power of 3 by 3 must be 0 (except 1). If the most basic factor of 3 is not divisible, it is definitely not the power of 3number.

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

The incoming parameter type is int. Some people may say that 1.0/9 is 3 to the power of -2, which is also a power of 3, but if you enter 1.0/9, the function will force the type to be converted to int.In fact, the operation into the function is 0,.

This function only determines whether a number greater than 0 is a power of 3.

leetcode的342. 4的幂 和3的幂思路相同