Combination Sum -- leetcode
来源:互联网 发布:太阳镜知乎 编辑:程序博客网 时间:2024/06/01 08:37
Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.
The same repeated number may be chosen from C unlimited number of times.
Note:
- All numbers (including target) will be positive integers.
- Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
- The solution set must not contain duplicate combinations.
For example, given candidate set 2,3,6,7
and target 7
,
A solution set is: [7]
[2, 2, 3]
该算法在leetcode上,实际运行时间为29ms。
基本思路为,candidates的每个元素选择合适的重复次数(包括0次),进行组合,看结果是否为target。
数组solution中元素的值,为对应的candidate元素的使用次数。
class Solution {public: vector<vector<int> > combinationSum(vector<int> &candidates, int target) { vector<vector<int> > result; sort(candidates.begin(), candidates.end()); vector<int> solution(candidates.size()); helper(result, solution, candidates, 0, target); return result; } void helper(vector<vector<int> >&result, vector<int> &solution, const vector<int> &candidates, int index, int target) { if (index == candidates.size()) return; solution[index] = 0; while (target > 0) { helper(result, solution, candidates, index+1, target); solution[index]++; target -= candidates[index]; } if (!target) { result.push_back(vector<int>()); for (int i=0; i<=index; i++) { for (int j=0; j<solution[i]; j++) { result.back().push_back(candidates[i]); } } } }};
以上算法参考自
https://oj.leetcode.com/discuss/20994/33ms-c-recursive-solution
他用了乘法和除法,每个元素的被使用的次数从最高到低递减偿试。
我将他的乘法和除法去掉,改成从低到高进行偿试。
原来算法的执行时间为33ms。我改后为29ms。 不知道这少掉的4ms是不是从剩法除法中挤出来的,或者是机器实际执行时间的随机性导致。
0 0
- [LeetCode] Combination Sum、Combination Sum II
- 【LeetCode】Combination Sum && Combination Sum II
- leetcode之Combination Sum && Combination Sum II
- leetcode Combination Sum &Combination Sum II
- leetcode-combination sum and combination sum II
- Leetcode:Combination Sum与Combination Sum II
- leetcode Combination Sum VS Combination Sum II
- [Leetcode]Combination Sum &&Combination Sum II
- LeetCode Combination Sum & Combination Sum II
- leetcode | Combination Sum & Combination Sum 2
- LeetCode: Combination Sum
- LeetCode: Combination Sum II
- LeetCode: Combination Sum
- LeetCode: Combination Sum II
- [LeetCode]Combination Sum
- [LeetCode]Combination Sum II
- LeetCode Combination Sum
- LeetCode Combination Sum II
- 数据库错误:Insert error 1064
- 【转】Opencv2系列学习笔记10(提取连通区域轮廓)
- linux安装完之后需要做的配置
- android 布局页面文件出错故障排除Exception raised during rendering: java.lang.System.arraycopy([CI[CII)V
- 各类 HTTP 返回状态代码详解
- Combination Sum -- leetcode
- Jfreechart创建环形图
- 对html实现监听 script脚本
- 内网与防火墙
- SQL SERVER 2008的EXCEPT和INTERSECT
- 关于2015年春运增开旅客列车的公告
- 如何查看dll文件
- JqGrid设置colModel自定义数据
- 解析XML数据