Subsets & Combinations - Letter Case Permutation
Given the partial output list from letter case permutation: ['a1b', 'a1B', 'A1b', 'A1B'], which of the following was the original input string?
Given the partial output list from letter case permutation: ['a1b', 'a1B', 'A1b', 'A1B'], which of the following was the original input string?
hard🔄 Reverse Engineer Q9 of Q15
Step-by-Step Solution
Solution:
Step 1: Analyze output variations
Output toggles cases of 'a' and 'b', digits unchanged.Step 2: Identify original input
Original input must be lowercase letters 'a' and 'b' with digit '1' unchanged -> "a1b".Final Answer:
Option B -> Option BQuick Check:
Output permutations match toggling letters in "a1b" [OK]
Quick Trick: Original input matches lowercase letters in output base [OK]
Common Mistakes:
MISTAKES- Assuming uppercase input
- Confusing output permutations with input
Trap Explanation:
PITFALL- Candidates often mistake output permutations as original input variants.
Interviewer Note:
CONTEXT- Tests reasoning backwards from output to input
Master "Letter Case Permutation" in Subsets & Combinations
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