题目介绍

解法

是77.组合链接的扩展

class Solution {
    List<List<Integer>> result= new ArrayList<>();
    List<Integer> path = new ArrayList<>();
    public List<List<Integer>> combinationSum3(int n, int k) {
        dfs(n, k, 1, 0);
        return result;
    }
    public void dfs(int targetSum, int k, int startIndex, int sum){
        if (path.size() == k){
            if (sum == targetSum){
                result.add(new ArrayList<>(path));
            }
            return;
        }
        for (int i = startIndex;i <= 9;i++){
            path.add(i);
            sum += i;
            dfs(targetSum, k, i + 1, sum);
            path.remove(path.size() - 1);
            sum -= i;
        }
    }
}