一个基本的回溯及其演变

 

void backtrace(vector<int>&record, vector<vector<int>>&res, int index, vector<int>path)
{
  if (path.size() == 2)
  {
    res.push_back(path);
    return;
  }
  for (int i = index; i < record.size(); i++)
  {
    path.push_back(record[i]);
    backtrace(record, res, i + 1, path);
    path.pop_back();
  }
}

int main()
{
  vector<int>record = { 5,4,3,2,1 };
  vector<vector<int>>res;
  vector<int>path;
  backtrace(record,res,0,path);
  cout << res.size() << endl;
  for (int i = 0; i < res.size(); i++)
  {
    for (int j = 0; j < res[0].size(); j++)
    {
      cout << res[i][j] << " ";
    }
    cout << endl;
  }
}

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 输出结果如下：

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​​77. 组合​​

​​面试题---求和​​

​​leetcode刷题之回溯，深度遍历​​