Subsets & Combinations - Subsets II (With Duplicates)
Given the final result of unique subsets: [[], [1], [2], [1,2], [2,2], [1,2,2]], which input array could have produced this output using the Subsets II pattern?
Given the final result of unique subsets: [[], [1], [2], [1,2], [2,2], [1,2,2]], which input array could have produced this output using the Subsets II pattern?
hard🔄 Reverse Engineer Q9 of Q15
Step-by-Step Solution
Solution:
Step 1: Analyze subsets containing duplicates
Subsets include [2,2] and [1,2,2], indicating input has two 2's.Step 2: Match input array
Only input [1,2,2] matches these subsets; [1,2,3] has no duplicates, [2,2,2] would have triple 2 subsets, [1,1,2] would have duplicates of 1.Final Answer:
Option B -> Option BQuick Check:
Subsets reflect exactly two 2's and one 1 [OK]
Quick Trick: Subsets with duplicates reveal input duplicates [OK]
Common Mistakes:
MISTAKES- Ignoring number of duplicates in input
- Confusing which element is duplicated
Trap Explanation:
PITFALL- Candidates often fail to reverse engineer input from subsets containing duplicates.
Interviewer Note:
CONTEXT- Tests deep understanding of subset generation and input-output relationship.
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