Connect 4

This is a simple terminal-based Connect 4 game for two players (X and O) on a 6 rows and 7 columns board.

How to Run

./connect4 <STONE>

• <STONE> is either X or O and specifies which stone the AI will play for this turn.
• If <STONE> is omitted, the AI defaults to O.

Protocol for Exchanging Turns

Board Representation

• The board is a 6-row by 7-column grid.
• Each cell is represented by a single character:
  • - (dash): empty cell
  • X: cell occupied by player X
  • O: cell occupied by player O
• Each row is printed on a separate line.
• Cells in a row are separated by a single space.
• No extra characters (such as | or prompts) are present in the input.

Example Board:

- - - - - - -
- - - - - - -
- - - - - - -
- - - - - - -
- - - X - - -
- O X O X O X

Turn Exchange

1. Input

• The program receives the current board state as described above, via standard input (stdin).
• The board must always have 6 rows and 7 columns, formatted as above.

2. Command Line Argument

• The program is invoked as: ./connect4 <STONE>
• <STONE> is either X or O and specifies which stone the AI will play for this turn.
• If <STONE> is omitted, the AI defaults to O.

3. AIs Move

• The program parses the board and determines the AI's move using its strategy.
• The AI always plays a single move for the specified stone.

4. Output

• The program outputs a single integer to standard output (stdout):
  • The column number (1-7, inclusive) where the AI will play its stone.
  • If there are no valid moves, the program outputs -1.
• No other output is produced.

Example Turn Exchange

Input (stdin):

- - - - - - -
- - - - - - -
- - - - - - -
- - - - - - -
- - - X - - -
- O X O X O X

Command:

./connect4 O

Output (stdout):

1

(Assuming the AI chose to play in the first column)

New Board State:

- - - - - - -
- - - - - - -
- - - - - - -
- - - - - - -
- - - X - - -
O O X O X O X

How to Play

• Players take turns entering the column number (1-7) to drop their piece.
• The first player is X, the second is O.
• The game ends when a player connects four in a row (horizontally, vertically, or diagonally) or the board is full (draw).