Leetcode Combination Sum

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] 

暴力搜索

class Solution {
public:
    vector<vector<int> > res;
    vector<int> path;
    vector<int> candidates;
    int target;
    
    void solve(int start, int sum){
        if(sum > target) return;
        if(sum == target){
            res.push_back(path);
            return;
        }
        for(int i = start; i < candidates.size(); ++ i){
            path.push_back(candidates[i]);
            solve(i,sum+candidates[i]);
            path.pop_back();
        }
    }

    vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
        this->candidates = candidates;
        this->target = target;
        sort(this->candidates.begin(),this->candidates.end());
        solve(0,0);
        return res;
    }
};