leetcode 216. Combination Sum III Add to List (枚举子集,限定集合大小,和为定值)

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。

 

leetcode 77. Combinations (枚举子集,限定集合大小)

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

 

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。

 

90. Subsets II (枚举子集)

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:

 

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。。