#include <iostream>
#include <vector>
#include <random>

using namespace std;

class Board
{
public:
  Board();

  char at(int x, int y) const;

  bool game_over(char& winner) const;
  void print() const;
  bool place_brick(int column, char player);

private:
  
  bool is_horizontal_win_at(int x, int y) const;
  bool is_vertical_win_at(int x, int y) const;
  bool is_down_right_diagonal_win_at(int x, int y) const;
  bool is_up_right_diagonal_win_at(int x, int y) const;
  bool is_full_board() const;
  
  using matrix = vector<vector<char> >;
  matrix board;
};

Board::Board() : board()
{
  for ( int row = 0; row < 7; row++ )
  {
    board.push_back(vector<char>(7, ' '));
  }
}

char Board::at(int x, int y) const
{
  if ( 0 <= x && x < 7 &&
       0 <= y && y < 7 )
    return board[y][x];
  else
    return ' ';
}

bool Board::is_horizontal_win_at(int x, int y) const
{
  char c = at(x, y);

  for ( int i = 1; i < 4; ++i )
  {
    if ( at(x + i, y) != c )
      return false;
  }
  return true;
}

bool Board::is_vertical_win_at(int x, int y) const
{
  char c = at(x, y);

  for ( int i = 1; i < 4; ++i )
  {
    if ( at(x, y + i) != c )
      return false;
  }
  return true;
}

bool Board::is_down_right_diagonal_win_at(int x, int y) const
{
  char c = at(x, y);

  for ( int i = 1; i < 4; ++i )
  {
    if ( at(x + i, y + i) != c )
      return false;
  }
  return true;
}

bool Board::is_up_right_diagonal_win_at(int x, int y) const
{
  char c = at(x, y);

  for ( int i = 1; i < 4; ++i )
  {
    if ( at(x + i, y - i) != c )
      return false;
  }
  return true;
}

bool Board::is_full_board() const
{
  for ( vector<char> const& row : board )
  {
    for ( char col : row )
    {
      if ( col == ' ' )
        return false;
    }
  }
  return true;
}

bool Board::game_over(char& winner) const
{
  for ( int x = 0; x < 7; ++x )
  {
    for ( int y = 0; y < 7; ++y )
    {
      if ( at(x, y) != ' ' )
      {
        if ( is_horizontal_win_at(x, y) ||
             is_vertical_win_at(x, y) ||
             is_down_right_diagonal_win_at(x, y) ||
             is_down_right_diagonal_win_at(x, y) )
        {
          winner = at(x, y);
          return true;
        }
      }
    }
  }

  if ( is_full_board() )
    return true;
  
  return false;
}

bool Board::place_brick(int column, char player)
{
  for ( matrix::reverse_iterator it = board.rbegin();
        it != board.rend(); ++it)
  {
    if ( it->at(column) == ' ' )
    {
      it->at(column) = player;
      return true;
    }
  }
  return false;
}

void Board::print() const
{
  cout << "|0123456|" << endl;
  for ( vector<char> const& row : board )
  {
    cout << '|';
    for ( char col : row )
    {
      cout << col;
    }
    cout << '|' << endl;
  }
  cout << "+-------+" << endl;
}

int main()
{
  Board board;
  
  char turn{'x'};
  char winner{' '};
  while ( ! board.game_over( winner ) )
  {
    int column;

    cout << turn << " chose column: ";
    cin >> column;
    cout << turn << " picked column " << column << endl;
    
    if ( board.place_brick( column, turn) )
    {
      board.print();

      if ( turn == 'x' )
        turn = 'o';
      else
        turn = 'x';
    }
  }

  if (winner == ' ')
    cout << "It's a draw." << endl;
  else
    cout << "'" << winner << "' wins!" << endl;
  
  cout << endl;

  return 0;
}