// Combination Sum II — MEDIUM

// Category: backtracking

Given a collection of candidate numbers (`candidates`) and a target number (`target`), find all unique combinations in `candidates` where the candidate numbers sum to `target`.

Each number in `candidates` may only be used **once** in the combination.

**Note:** The solution set must not contain duplicate combinations. Sort first to skip duplicates.

Example: candidates = [10,1,2,7,6,1,5], target = 8

Output: [[1,1,6],[1,2,5],[1,7],[2,6]]