Base 7 — LeetCode 504 Python Solution

The problem

Given an integer num, return a string of its base 7 representation.

Example

Input

num = 100

Output

"202"

Python solution

class Solution:
    def convertToBase7(self, num: int) -> str:
        if num == 0:
            return '0'
        if num < 0:
            return '-' + self.convertToBase7(-num)
        ans = []
        while num:
            ans.append(str(num % 7))
            num //= 7
        return ''.join(ans[::-1])

Complexity

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 504. Base 7 is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Math.

The math and number theory guide has the Python template for the pattern and the 485 LeetCode problems that use it.

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