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class Solution {
public:

    void Help(vector<vector<int>>& results, vector<int>& result, vector<int>& num, vector<int>& flags)
    {
        if (result.size() == num.size())
        {
            results.push_back(result);
            return;
        }

        for (int i = 0; i < flags.size(); i++)
        {
            if (flags[i] == 0)  //跳过已经取过的数
                continue;

            result.push_back(num[i]);
            flags[i] = 0;
            Help(results, result, num, flags);
            flags[i] = 1;
            result.pop_back();
        }
    }

    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int>> results;
        vector<int> result;
        vector<int> flags(nums.size(), 1);;
        Help(results, result, nums, flags);

        return results;
    }
};

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class Solution {
public:

    void FindAll(vector<int>& candidates, vector<vector<int>>& results, vector<int> &result, int &current, int &target, int id)
    {
        if (current == target)
        {
            results.push_back(result);
            return;
        }

        for (int i = id; i < candidates.size(); i++)
        {
            if (candidates[i]  <= target - current )
            {
                result.push_back(candidates[i]);
                current += candidates[i];
                FindAll(candidates, results, result, current, target, i);
                current -= candidates[i];
                result.pop_back();
            }
            else
            {
                break;
            }
        }
    }

    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {

        vector<vector<int>> results;
        vector<int> result;
        int current = 0;

        FindAll(candidates, results, result, current, target, 0);

        return results;
    }
};