代码随想录算法训练营第二十四天| 77. 组合

77.组合

public  List<List<Integer>> combine(int n, int k) {if (n < k) {return null;}List<List<Integer>> list = new ArrayList<>();List<Integer> path = new ArrayList<>();backSource(n, path, list, k);return list;}public  void backSource(int n, List<Integer> path, List<List<Integer>> list, int k) {if (path.size() > k) {return;}if (path.size() == k) {list.add(new ArrayList<>(path));return;}for (int i = 1; i <= n; i++) {if (!path.contains(i)) {path.add(i);backSource(i, path, list, k);path.remove(path.size() - 1);}}}