题解 | #加起来和为目标值的组合(三)#

class Solution {
private:
    vector<vector<int>> res;
    vector<int> path;
    int cur_k = 0;
    int cur_tar = 0;
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param k int整型 
     * @param n int整型 
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > combination(int k, int n) {
        // write code here
        if(n > 45){
            return {};
        }
        
        vector<int> nums =  {1,2,3,4,5,6,7,8,9};
        dfs(nums, n, k, 0);
        return res;
    }
    
    void dfs(vector<int>& nums, int n, int k, int cur_i){
        if(cur_tar > n || cur_k > k){
            return;
        }
        
        if(cur_tar == n && cur_k == k){
            res.push_back(path);
            return;
        }
        
        for(int i=cur_i; i<nums.size(); i++){
            path.push_back(nums[i]);
            cur_k += 1;
            cur_tar += nums[i];
            
            dfs(nums, n, k, i+1);
            
            path.pop_back();
            cur_k -= 1;
            cur_tar -= nums[i];
        }
        
    }
    
};