private void recur(level, params) {
  // 1. terminator
  if (level > MAX_LEVEL) {
    process_result();
    return;
  }
  // 2. prepare data
  prepare_data(parmas);
  // 3. drill down
  recur(level+1, newParams);
  // 4. restore current status
  restore(params);
}

private void divide_conquer(problem, params) {
  // 1. terminator    
  if (problem == NULL) {    
    process_last_result();    
    return;       
  }  

  // 2. prepare data
  data = prepare_data(problem)
  subProblems = split_problem(problem, data);
  
  // 3. drill down
  // 3.1 (conquer subproblems)
  subresult0 = divide_conquer(subProblems[0]);
  subresult1 = divide_conquer(subProblems[1]); 
  ...
   
  // 3.2 process and generate the final result for current level.(merge subresults)
  result = process_result(res0, res1);    

  // 4. restore current level status
  restore(params);
}

result = []
def backtrack(path,选择列表):
    if 满足结束条件:
        res.add(path)
        return

    for 选择 in 选择列表:
        # 做选择
        将该选择从选择列表移除
        path.add(选择)
        backtrack(路径, 选择列表)
        # 撤销选择
        path.remove(选择)
        将该选择重新加入选择列表