一:题目

二:上码

class Solution {/**递归深度根据k值确定,宽度的话那就[1,9]因为递归不允许重复，那么的话我们需要每次在横向遍历的起始位置+1*/private List<List<Integer>> ans = new ArrayList<>();private List<Integer> path = new ArrayList<>();public int getSum(List<Integer> 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<List<Integer>> combinationSum3(int k, int n) {getAns(1,k,n);return ans;}
}