Power of Three Python Solution with Tests

Tested Python solution for LeetCode 326 with 20 pytest cases. Generate a practice environment with lcpy.

LeetCode 326, Easy. Topics: Math, Recursion. View on LeetCode.

Generate this problem as a practice environment: tested reference solution, 20 parametrized pytest cases, and a playground notebook:

lcpy gen -n 326   # by problem number
lcpy gen -s power_of_three   # by problem name

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Problem

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 == 3^x.

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Examples

Input: n = 27
Output: true
Explanation: 27 = 3^3

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

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

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Constraints

• -2^31 <= n <= 2^31 - 1

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

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Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

class Solution:
    # Time: O(1)
    # Space: O(1)
    def is_power_of_three(self, n: int) -> bool:
        # 3^19 = 1162261467 is the largest power of three fitting in a signed
        # 32-bit int; it is divisible by every smaller power of three and by
        # no other positive integer in range. Constant time, no loops.
        return n > 0 and 1162261467 % n == 0

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Complexity

Time	Space
O(1)	O(1)

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