LeetCode 39. Combination Sum

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.

For example, given candidate set [2, 3, 6, 7] and target 7, 
A solution set is: 

[  [7],  [2, 2, 3]]

递归求解

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class Solution {public:    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {        dfs(candidates,0,0,target);        return v;    }private:    vector<vector<int>> v;    vector<int> r;    void dfs(vector<int> vv,int index,int sum,int target){                if(sum>target) return;        if(sum==target) v.push_back(r);        if(index>target) return;        for(int i=0;i<vv.size();i++){            r.push_back(vv[i]);            if(index>=1&&r[index]<r[index-1]) {                r.pop_back();                continue;            }            dfs(vv,index+1,sum+vv[i],target);            r.pop_back();        }    }};