LeetCode #39 - Combination Sum - Medium
来源:互联网 发布:工艺流程图制作软件 编辑:程序博客网 时间:2024/05/26 19:18
Combination Sum Series
Combination Sum I: http://blog.csdn.net/Arcome/article/details/53888879
Combination Sum II:
Combination Sum III: http://blog.csdn.net/Arcome/article/details/53758448
Problem
Given a set of candidate numbers (C) (without duplicates) 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.
- The solution set must not contain duplicate combinations.
Example
For example, given candidate set [2, 3, 6, 7] and target 7, A solution set is: [ [7], [2, 2, 3]]
Algorithm
整理一下题意: 给定一个正整数集合C和一个目标数T,要求找到所有来自C的组合,使得组合的和等于T。C中的元素可以重复选择。
使用回溯法的经典题目。一开始陷入了subsets问题类似的思路中,没有回过来,所以想了好几种解法,要么是缺了部分组合,要么是出现了重复的组合,都没有AC。
重新整理思路后,在回溯的框架下思考。
由于candidates中的元素可以重复选,所以递归调用生成函数时应该不用对candidates的元素进行添加或删减操作。那么每次递归调用生成的区别应该在于新旧target的不同。同时,增加一个新的参数index,表示当前回溯到达的层次。
使用index的好处使得相同元素可以重复选。
代码如下。
class Solution {public: vector<vector<int>> combinationSum(vector<int>& candidates, int target) { vector<int> temp; vector<vector<int>> result; sort(candidates.begin(),candidates.end()); generate(temp,result,candidates,target,0); return result; } void generate(vector<int> temp,vector<vector<int>>&result,vector<int> candidates,int target,int index){ if(target==0){ result.push_back(temp); return; } for(int i=index;i<candidates.size();i++){ if(target>=candidates[i]){ temp.push_back(candidates[i]); generate(temp,result,candidates,target-candidates[i],i); temp.pop_back(); } } }};
0 0
- [Leetcode 39, Medium] Combination Sum
- LeetCode #39 - Combination Sum - Medium
- LeetCode-39-Combination Sum(DFS)-Medium
- Medium 39题 Combination Sum
- [Leetcode 40, Medium] Combination Sum II
- [Leetcode 216, Medium] Combination sum III
- [LeetCode] 039. Combination Sum (Medium) (C++)
- [leetcode] 040. Combination Sum II (Medium) (C++)
- Leetcode 39. Combination Sum (Medium) (cpp)
- Leetcode 40. Combination Sum II (Medium) (cpp)
- Leetcode 216. Combination Sum III (Medium) (cpp)
- 216.leetcode Combination Sum III(medium)[回溯]
- 39.leetcode Combination Sum(medium)[递归回溯]
- Leetcode 377. Combination Sum IV (Medium) (cpp)
- Leetcode 39. Combination Sum (Medium) (java)
- Leetcode 40. Combination Sum II (Medium) (java)
- (Leetcode)377. Combination Sum IV (medium)
- LeetCode[377. Combination Sum IV] 难度[medium]
- 大数据Spark “蘑菇云”行动第106课:Hive源码大师之路第四步:Hive中GroupBy和各种类型Join源码剖析
- bzoj4498
- 4555: [Tjoi2016&Heoi2016]求和
- 使用正则表达式解析语句
- 【SSH】开发环境搭建
- LeetCode #39 - Combination Sum - Medium
- 玲珑杯 1074 - Pick Up Coins (选硬币 || 区间DP)
- 如何添加Plugin及extentions,博主文章也不错
- Python 12.26
- [JZOJ4931] A
- UML类图几种关系的总结
- 从命令行运行 MyBatis Generator
- 自己写个 字典解析为模型的库
- 对 Java 中 clone 方法的思考