License Key Formatting — LeetCode 482 Python Solution

The problem

You are given a license key represented as a string s that consists of only alphanumeric characters and dashes. The string is separated into n + 1 groups by n dashes.

Example

Input

s = "5F3Z-2e-9-w", k = 4

Output

"5F3Z-2E9W"

Explanation

The string s has been split into two parts, each part has 4 characters.

Python solution

class Solution:
    def licenseKeyFormatting(self, s: str, k: int) -> str:
        n = len(s)
        cnt = (n - s.count("-")) % k or k
        ans = []
        for i, c in enumerate(s):
            if c == "-":
                continue
            ans.append(c.upper())
            cnt -= 1
            if cnt == 0:
                cnt = k
                if i != n - 1:
                    ans.append("-")
        return "".join(ans).rstrip("-")

Complexity

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 482. License Key Formatting is filed here because the reference solution below belongs to the algorithm family this hub collects, even though its LeetCode tags point elsewhere.

The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.

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