LeetCode CombinationSum

class Solution {
public:
    vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
        
        sort(candidates.begin(), candidates.end());
        candidates.erase(unique(candidates.begin(), candidates.end()), candidates.end());
        
        vector<vector<int> > tmp;
        vector<int> sel;
        
        dfs(candidates, 0, target, sel, tmp);
        return tmp;
    }
    
    void dfs(vector<int>& nums, int pos, int tar, vector<int>& sel, vector<vector<int> >& res) {
        if (tar == 0) {
            res.push_back(sel);
            return;
        }
        if (pos >= nums.size()) return;
        int cur = nums[pos];
        int add = 0;
        for (add = 0; add <= tar; add+=cur) {
            if (add != 0) {
                sel.push_back(cur);
            }
            dfs(nums, pos + 1, tar - add, sel, res);
        }
        for (int i = add/cur - 1; i>0; i--) {
            sel.pop_back();
        }
    }
};

dfs搜索，通过unique操作去除重复的候选数字，避免产生重复的序列