LeetCode 2325: Decode the Message ·

Table of Contents

Meta Data
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Difficulty: easy
First Attempt: 2025-04-22

Total time: 10:00.00

Intuition
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We can build a mapping from each character in the key to a corresponding character starting from 'a' by using ord().
After constructing the substitution table, we simply iterate through the message and join the result.
This is an O(n) solution that iterates through the array once.

Approach
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class Solution:
    def decodeMessage(self, key: str, message: str) -> str:
        idx_map = {}
        first_ord = 97  # ASCII code for 'a'
        for s in key:
            if s != " " and s not in idx_map:
                idx_map[s] = chr(first_ord)
                first_ord += 1
        return "".join(idx_map[s] if s != " " else s for s in message)