README_EN.md

326. Power of Three

中文文档

Description

Given an integer n, return true if it is a power of three. Otherwise, return false.

An integer n is a power of three, if there exists an integer x such that n == 3x.

 

Example 1:

Input: n = 27
Output: true
Explanation: 27 = 33

Example 2:

Input: n = 0
Output: false
Explanation: There is no x where 3x = 0.

Example 3:

Input: n = -1
Output: false
Explanation: There is no x where 3x = (-1).

 

Constraints:

• -231 <= n <= 231 - 1

 

Follow up: Could you solve it without loops/recursion?

Solutions

Python3

class Solution:
    def isPowerOfThree(self, n: int) -> bool:
        while n > 2:
            if n % 3:
                return False
            n //= 3
        return n == 1

class Solution:
    def isPowerOfThree(self, n: int) -> bool:
        return n > 0 and 1162261467 % n == 0

Java

class Solution {
    public boolean isPowerOfThree(int n) {
        while (n > 2) {
            if (n % 3 != 0) {
                return false;
            }
            n /= 3;
        }
        return n == 1;
    }
}

class Solution {
    public boolean isPowerOfThree(int n) {
        return n > 0 && 1162261467 % n == 0;
    }
}

C++

class Solution {
public:
    bool isPowerOfThree(int n) {
        while (n > 2) {
            if (n % 3) {
                return false;
            }
            n /= 3;
        }
        return n == 1;
    }
};

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

Go

func isPowerOfThree(n int) bool {
	for n > 2 {
		if n%3 != 0 {
			return false
		}
		n /= 3
	}
	return n == 1
}

func isPowerOfThree(n int) bool {
	return n > 0 && 1162261467%n == 0
}

TypeScript

function isPowerOfThree(n: number): boolean {
    return n > 0 && 1162261467 % n == 0;
}

JavaScript

/**
 * @param {number} n
 * @return {boolean}
 */
var isPowerOfThree = function (n) {
    return n > 0 && 1162261467 % n == 0;
};

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