Combination Sum II
Given an array of integers and a target Return all unique combinations that sum to the target Each number can be used at most ONCE Example: candidates = [10,1,2,7,6,1,5], target = 8 => [[1,1,6],[1,2,5],[1,7],[2,6]]
Combination Sum II rewards structured search and good pruning more than raw cleverness. Interviewers love it because it reveals your structured exploration and your edge-case discipline. Backtracking gets messy when you don't undo state cleanly; be disciplined about it.
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