leetcode 40. Combination Sum II (枚举子集，和为定值)

  * Total Accepted: **106670**
  * Total Submissions: **329718**
  * Difficulty: **Medium**
  * Contributor: **LeetCode**

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

Each number in C 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.

题意：若干正数，求所有和为target的组合。

思路：枚举子集，用和剪枝。