leetcode216. 组合总和 III

class Solution {
    
    private List> ans = new ArrayList<>();
    private List path = new ArrayList<>();
    
    public int getSum(List list) {
        int sum = 0;
        for (Integer nums:list) {
            sum += nums;
        }
        return sum;
    }

    public void getAns(int st,int k,int n) {
        
        if (path.size() == k) {
            if (getSum(path) == n) ans.add(new ArrayList<>(path)); 
            return ;
        }

        for (int i = st; i <= 9; i++) {
            path.add(i);
            getAns(i+1,k,n);
            path.remove(path.size()-1);
        }

    }

    public List> combinationSum3(int k, int n) {
        getAns(1,k,n);
        return ans;
    }
}