Power of Three

Problem

Return true iff n is a power of three.

Constraints

• -2³¹ ≤ n ≤ 2³¹−1

Approach — Core Patterns

This is a Core Patterns problem. The idea: pick the data structure best matched to the constraints and solve it in one clean pass. Work through the reference code below line by line, then re-derive it yourself in the editor — that's how the pattern sticks.

Complexity: see the walkthrough below.

Solution code

Python

class Solution:
    def isPowerOfThree(self, n):
        if n < 1:
            return False
        while n % 3 == 0:
            n //= 3
        return n == 1

Java

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

Practice it

Reading a solution isn't the same as being able to write it under pressure. Open this problem in the in-browser editor, hide the solution, and solve it from scratch — your code runs against real test cases instantly.