326

326. Power of Three (Easy)

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

Example 2:

Input: n = 0
Output: false

Example 3:

Input: n = 9
Output: true

Example 4:

Input: n = 45
Output: false

 

Constraints:

• -231 <= n <= 231 - 1

 

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

Related Topics:
Math

Similar Questions:

• Power of Two (Easy)
• Power of Four (Easy)
• Check if Number is a Sum of Powers of Three (Medium)

Solution 1.

// OJ: https://leetcode.com/problems/power-of-three/
// Author: github.com/lzl124631x
// Time: O(log3(N))
// Space: O(1)
class Solution {
public:
    bool isPowerOfThree(int n) {
        if (n < 1) return false;
        while (n % 3 == 0) n /= 3;
        return n == 1;
    }
};

Solution 2.

// OJ: https://leetcode.com/problems/power-of-three/
// Author: github.com/lzl124631x
// Time: O(log10(N))
// Space: O(1)
class Solution {
public:
    bool isPowerOfThree(int n) {
        return n < 1 ? false : fmod(log10(abs(n))/log10(3), 1) == 0;
    }
};

Solution 3.

// OJ: https://leetcode.com/problems/power-of-three/solution/
// Author: github.com/lzl124631x
// Time: O(1)
// Space: O(1)
class Solution {
public:
    bool isPowerOfThree(int n) {
        return n > 0 && 1162261467 % n == 0;
    }
};