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0040-combination-sum-ii.adoc

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40. Combination Sum II

{leetcode}/problems/combination-sum-ii/[LeetCode - Combination Sum II^]

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

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

Note:

  • All numbers (including target) will be positive integers.

  • The solution set must not contain duplicate combinations.

Example 1:
Input: candidates = [10,1,2,7,6,1,5], target = 8,
A solution set is:
[
  [1, 7],
  [1, 2, 5],
  [2, 6],
  [1, 1, 6]
]
Example 2:
Input: candidates = [2,5,2,1,2], target = 5,
A solution set is:
[
  [1,2,2],
  [5]
]

思路分析

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这道题的关键是由于候选值不能重复使用，所以需要向下传递起始位置。可以对比一下 39. Combination Sum 的处理上的不同之处。

思考一下解决重复值时是怎么剪枝的？

一刷
link:{sourcedir}/_0040_CombinationSumII.java[role=include]
二刷
link:{sourcedir}/_0040_CombinationSumII_2.java[role=include]
三刷
link:{sourcedir}/_0040_CombinationSumII_3.java[role=include]