Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.

题意：1..9个数，从中选择k个，和为n，要求输出所有满足题意的集合。

思路：枚举子集，根据sum和集合元素个数剪枝即可。

Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.

思路：就是枚举子集，根据集合的大小剪枝。。。最后只要集合大小为k的集合

 1/* ***********************************************
 2Author :111qqz
 3Created Time :2017年04月13日 星期四 15时25分37秒
 4File Name :77.cpp
 5************************************************ */
 6class …

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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 …

Given a collection of integers that might contain duplicates, nums, return all possible subsets.

Note: The solution set must not contain duplicate subsets.

For example, If nums = [1,2,2], a solution is:

[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

思路：

复习（？）一下 枚举子集的三种写法

（还有种更飘逸的...先不写了orz

这道题我用位向量法A的。。