前言
【LeetCode 题解】系列传送门: http://www.cnblogs.com/double-win/category/573499.html
1.题目描述
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]
2. 题意
给定一个候选集合,集合中的元素以非递减方式存放。给定一个目标值T。
输出所有唯一的组合。
3. 思路
由于不能出现重复元组,所以我们先将candidate set进行排序,然后规定比新插入的元素不能比当前元素小。
采用DFS思想即可。
4: 解法
class Solution {
private:
vector<int> ans;
vector<vector<int> > ret;
public:
void DFS(int start,vector<int> &candidates, int target){
if(target==0){
ret.push_back(ans);
return;
} for(int i=start;i<candidates.size();++i){
if(target <candidates[i]) return;
ans.push_back(candidates[i]);
DFS(i,candidates,target-candidates[i]);
ans.pop_back();
}
}
vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
ans.clear();
ret.clear();
if(!target || !candidates.size()) return ret;
sort(candidates.begin(),candidates.end());
DFS(0,candidates,target);
return ret;
}
};
作者:Double_Win 出处: http://www.cnblogs.com/double-win/p/3896010.html 声明: 由于本人水平有限,文章在表述和代码方面如有不妥之处,欢迎批评指正~ |