comefrom: <awangdev>Combination Sum III_1.java
code: private void dfs(List<List<Integer>> result, List<Integer> list,
  
                       int index, int k, int n) {
          for (int i = index; i <= 9; i++) {
              list.add(i);
              if (n == i && list.size() == k) { 
                  result.add(new ArrayList<>(list));
              } else if (n > i){
                  dfs(result, list, i + 1, k, n - i);
              }
              list.remove(list.size() - 1);
          }
      }
masked: private void sample_funcname ( List < List < Integer >> result , List < Integer > list , int index , int k , int n ) {
    for ( int i = index ;
    i <= 9 ;
    i ++ ) {
      list . add ( i ) ;
      if ( n == i && list . size ( ) == k ) {
        result . add ( new ArrayList < > ( list ) ) ;
      }
      else if ( n > i ) {
        dfs ( result , list , i + 1 , k , n - i ) ;
      }
      list . remove ( list . size ( ) - 1 ) ;
    }
  }
  