Reviewed by Aditya Kumar · Last reviewed 2026-03-24
To identify pairs of strings that, when concatenated, contain all 26 English alphabets, the most efficient approach involves representing each string's unique character set as a bitmask. This allows…
This easy-level Python/Coding question appears frequently in data engineering interviews at companies like JP Morgan. While less common, it tests deeper understanding that distinguishes strong candidates.
Start by clearly defining the core concept being asked about. Interviewers want to see that you understand the fundamentals before diving into implementation details. Structure your answer with a definition, then explain the practical application with a concise example.
To identify pairs of strings that, when concatenated, contain all 26 English alphabets, the most efficient approach involves representing each string's unique character set as a bitmask. This allows for constant-time set union and comparison, significantly optimizing the search.
Each of the 26 English alphabets (a-z) maps to a unique bit position (e.g., 'a' to the 0th bit, 'b' to the 1st bit). A string's character set is represented by a 26-bit integer (bitmask) where the i-th bit is set if the i-th alphabet is present. The target mask for all 26 alphabets is (1 << 26) - 1.
The optimized algorithm proceeds as follows:
Pro-Move: Bitmask optimization. Red Flag: O(n²) when n large.
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According to DataEngPrep.tech, this is one of the most frequently asked Python/Coding interview questions, reported at 1 company. DataEngPrep.tech maintains an editor-reviewed database of 1,863 data engineering interview questions across 7 categories.