Subsets & Combinations - Combinations (Choose K from N)
Given the partial output of a backtracking call stack generating combinations of size 3 from 1 to 5, the current path is [2, 4]. Which element is the next valid candidate to add?
Given the partial output of a backtracking call stack generating combinations of size 3 from 1 to 5, the current path is [2, 4]. Which element is the next valid candidate to add?
hard🔄 Reverse Engineer Q9 of Q15
Step-by-Step Solution
Solution:
Step 1: Understand backtracking start index
Next candidates must be greater than last element in path (4) to maintain ascending order.Step 2: Identify valid next elements
From 1 to 5, only 5 is greater than 4 and valid to add next.Final Answer:
Option A -> Option AQuick Check:
Next candidate must be > 4, so 5 is correct [OK]
Quick Trick: Next candidate > last path element [OK]
Common Mistakes:
MISTAKES- Choosing smaller or equal elements
- Ignoring ascending order constraint
Trap Explanation:
PITFALL- Candidates often forget to enforce ascending order in combinations generation.
Interviewer Note:
CONTEXT- Tests deep understanding of backtracking candidate selection logic.
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