Decrypt String from Alphabet to Integer Mapping — LeetCode 1309 Python Solution

The problem

You are given a string s formed by digits and '#'. We want to map s to English lowercase characters as follows: Characters ('a' to 'i') are represented by ('1' to '9') respectively.

Example

Input

s = "10#11#12"

Output

"jkab"

Explanation

"j" -> "10#" , "k" -> "11#" , "a" -> "1" , "b" -> "2".

Python solution

class Solution:
    def freqAlphabets(self, s: str) -> str:
        ans = []
        i, n = 0, len(s)
        while i < n:
            if i + 2 < n and s[i + 2] == "#":
                ans.append(chr(int(s[i : i + 2]) + ord("a") - 1))
                i += 3
            else:
                ans.append(chr(int(s[i]) + ord("a") - 1))
                i += 1
        return "".join(ans)

Complexity

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 1309. Decrypt String from Alphabet to Integer Mapping 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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