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pdagosta
2022-03-05 11:07:45 -06:00
parent 1e802915e5
commit 95fa8e7da3
1 changed files with 379 additions and 208 deletions
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587
23_Checkers/csharp/Program.cs
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@@ -1,33 +1,28 @@
const int LineLength = 80;
Dictionary<int, string> Pieces = new Dictionary<int, string>()
{
{ -2, "X*" },
{ -1, "X " },
{ 0, ". " },
{ 1, "O " },
{ 2, "O*" },
};
void PrintBoard(int[,] state)
{
SkipLines(3);
for (int y = 7; y >= 0; y--)
{
for (int x = 0; x < 8; x++)
{
Console.Write(Pieces[state[x, y]]);
Console.Write(" ");
}
Console.WriteLine();
}
}
void WriteCenter(string text)
{
var spaces = (LineLength - text.Length) / 2;
Console.WriteLine($"{"".PadLeft(spaces)}{text}");
}
/*********************************************************************************
* CHECKERS
* ported from BASIC https://www.atariarchives.org/basicgames/showpage.php?page=41
*
* Porting philosophy
* 1) Adhere to the original as much as possible
* 2) Attempt to be understandable by Novice progammers
*
* There are no classes or Object Oriented design patterns used in this implementation.
* Everything is written procedurally, using only top-level functions. Hopefully, this
* will be approachable for someone who wants to learn C# syntax without experience with
* Object Oriented concepts. Similarly, basic data structures have been chosen over more
* powerful collection types. Linq/lambda syntax is also excluded.
*
* C# Concepts contained in this example:
* Loops (for, foreach, while, and do)
* Multidimensional arrays
* Tuples
* Nullables
* IEnumerable (yield return / yield break)
*
* The original had multiple implementations of logic, like determining second jump locations.
* This has been refactored to reduce unnecessary code duplication.
*********************************************************************************/
#region Display functions
void SkipLines(int count)
{
for (int i = 0; i < count; i++)
@@ -36,6 +31,72 @@ void SkipLines(int count)
}
}
void PrintBoard(int[,] state)
{
SkipLines(3);
for (int y = 7; y >= 0; y--)
{
for (int x = 0; x < 8; x++)
{
switch(state[x,y])
{
case -2:
Console.Write("X*");
break;
case -1:
Console.Write("X ");
break;
case 0:
Console.Write(". ");
break;
case 1:
Console.Write("O ");
break;
case 2:
Console.Write("O*");
break;
}
Console.Write(" ");
}
Console.WriteLine();
}
}
void WriteCenter(string text)
{
const int LineLength = 80;
var spaces = (LineLength - text.Length) / 2;
Console.WriteLine($"{"".PadLeft(spaces)}{text}");
}
void ComputerWins()
{
Console.WriteLine("I WIN.");
}
void PlayerWins()
{
Console.WriteLine("YOU WIN.");
}
void WriteIntroduction()
{
WriteCenter("CHECKERS");
WriteCenter("CREATIVE COMPUTING MORRISTOWN, NEW JERSEY");
SkipLines(3);
Console.WriteLine("THIS IS THE GAME OF CHECKERS. THE COMPUTER IS X,");
Console.WriteLine("AND YOU ARE O. THE COMPUTER WILL MOVE FIRST.");
Console.WriteLine("SQUARES ARE REFERRED TO BY A COORDINATE SYSTEM.");
Console.WriteLine("(0,0) IS THE LOWER LEFT CORNER");
Console.WriteLine("(0,7) IS THE UPPER LEFT CORNER");
Console.WriteLine("(7,0) IS THE LOWER RIGHT CORNER");
Console.WriteLine("(7,7) IS THE UPPER RIGHT CORNER");
Console.WriteLine("THE COMPUTER WILL TYPE '+TO' WHEN YOU HAVE ANOTHER");
Console.WriteLine("JUMP. TYPE TWO NEGATIVE NUMBERS IF YOU CANNOT JUMP.");
SkipLines(3);
}
#endregion
#region State validation functions
bool IsPointOutOfBounds(int x)
{
return x < 0 || x > 7;
@@ -46,15 +107,152 @@ bool IsOutOfBounds((int x, int y) position)
return IsPointOutOfBounds(position.x) || IsPointOutOfBounds(position.y);
}
bool IsJumpMove((int x, int y) from, (int x, int y) to)
{
return Math.Abs(from.y - to.y) == 2;
}
bool IsValidPlayerMove(int[,] state, (int x, int y) from, (int x, int y) to)
{
if (state[to.x, to.y] != 0)
{
return false;
}
var deltaX = Math.Abs(to.x - from.x);
var deltaY = Math.Abs(to.y - from.y);
if (deltaX != 1 && deltaX != 2)
{
return false;
}
if (deltaX != deltaY)
{
return false;
}
if (state[from.x, from.y] == 1 && Math.Sign(to.y - from.y) <= 0)
{
// only kings can move downwards
return false;
}
if (deltaX == 2)
{
var jump = GetJumpedPiece(from, to);
if (state[jump.x, jump.y] >= 0)
{
// no valid piece to jump
return false;
}
}
return true;
}
bool CheckForComputerWin(int[,] state)
{
bool playerAlive = false;
foreach (var piece in state)
{
if (piece > 0)
{
playerAlive = true;
break;
}
}
return !playerAlive;
}
bool CheckForPlayerWin(int[,] state)
{
bool computerAlive = false;
foreach (var piece in state)
{
if (piece < 0)
{
computerAlive = true;
break;
}
}
return !computerAlive;
}
#endregion
#region Board "arithmetic"
/// <summary>
/// Get the Coordinates of a jumped piece
/// </summary>
(int x, int y) GetJumpedPiece((int x, int y) from, (int x, int y) to)
{
var midX = (to.x + from.x) / 2;
var midY = (to.y + from.y) / 2;
return (midX, midY);
}
/// <summary>
/// Apply a directional vector "direction" to location "from"
/// return resulting location
/// direction will contain: (-1,-1), (-1, 1), ( 1,-1), ( 1, 1)
/// /// </summary>
(int x, int y) GetLocation((int x , int y) from, (int x, int y) direction)
{
return (x: from.x + direction.x, y: from.y + direction.y);
}
#endregion
#region State change functions
/// <summary>
/// Alter current "state" by moving a piece from "from" to "to"
/// This method does not verify that the move being made is valid
/// This method works for both player moves and computer moves
/// </summary>
int[,] ApplyMove(int[,] state, (int x, int y) from, (int x, int y) to)
{
state[to.x, to.y] = state[from.x, from.y];
state[from.x, from.y] = 0;
if (IsJumpMove(from, to))
{
// a jump was made
// remove the jumped piece from the board
var jump = GetJumpedPiece(from, to);
state[jump.x, jump.y] = 0;
}
return state;
}
/// <summary>
/// At the end of a turn (either player or computer) check to see if any pieces
/// reached the final row. If so, change them to kings (crown)
/// </summary>
int[,] CrownKingPieces(int[,] state)
{
for (int x = 0; x < 8; x++)
{
// check the bottom row if computer has a piece in it
if (state[x, 0] == -1)
{
state[x, 0] = -2;
}
// check the top row if the player has a piece in it
if (state[x, 7] == 1)
{
state[x, 7] = 2;
}
}
return state;
}
#endregion
#region Computer Logic
/// <summary>
/// Given a current location "from", determine if a move exists in a given vector, "direction"
/// direction will contain: (-1,-1), (-1, 1), ( 1,-1), ( 1, 1)
/// return "null" if no move is possible in this direction
/// </summary>
(int x, int y)? GetCandidateMove(int[,] state, (int x, int y) from, (int x, int y) direction)
{
var to = (x: from.x + direction.x, y: from.y + direction.y);
var to = GetLocation(from, direction);
if (IsOutOfBounds(to))
return null;
if (state[to.x, to.y] > 0)
{
// potential jump
to = (x: to.x + direction.x, y: to.y + direction.y);
to = GetLocation(to, direction);
if (IsOutOfBounds(to))
return null;
}
@@ -64,12 +262,11 @@ bool IsOutOfBounds((int x, int y) position)
return to;
}
bool IsJumpMove((int x, int y) from, (int x, int y) to)
{
return Math.Abs(from.y - to.y) == 2;
}
int AnalyzeMove(int[,] state, (int x, int y) from, (int x, int y) to)
/// <summary>
/// Calculate a rank for a given potential move
/// The higher the rank value, the better the move is considered to be
/// </summary>
int RankMove(int[,] state, (int x, int y) from, (int x, int y) to)
{
int rank = 0;
@@ -90,12 +287,13 @@ int AnalyzeMove(int[,] state, (int x, int y) from, (int x, int y) to)
}
if (to.x == 0 || to.x == 7)
{
// move to edge
// move to edge of board
rank += 1;
}
for (int c = -1; c <=1; c++)
// look to the row in front of the potential destination for
for (int c = -1; c <=1; c+=2)
{
var inFront = (x: to.x + c, y: to.y - 1);
var inFront = GetLocation(to, (c, -1));
if (IsOutOfBounds(inFront))
continue;
if (state[inFront.x, inFront.y] < 0)
@@ -104,13 +302,13 @@ int AnalyzeMove(int[,] state, (int x, int y) from, (int x, int y) to)
rank++;
continue;
}
var inBack = (x: to.x - c, y: to.y + 1);
var inBack = GetLocation(to, (-c, 1));
if (IsOutOfBounds(inBack))
{
continue;
}
if (inBack == from ||
(state[inFront.x, inFront.y] > 0 && state[inBack.x, inBack.y] == 0))
if ((state[inFront.x, inFront.y] > 0) &&
(state[inBack.x, inBack.y] == 0) || (inBack == from))
{
// the player can jump us
rank -= 2;
@@ -119,6 +317,10 @@ int AnalyzeMove(int[,] state, (int x, int y) from, (int x, int y) to)
return rank;
};
/// <summary>
/// Returns an enumeration of possible moves that can be made by the given piece "from"
/// If no moves, can be made, the enumeration will be empty
/// </summary>
IEnumerable<(int x, int y)> GetPossibleMoves(int[,] state, (int x, int y) from)
{
int maxB;
@@ -156,7 +358,10 @@ IEnumerable<(int x, int y)> GetPossibleMoves(int[,] state, (int x, int y) from)
}
}
}
/// <summary>
/// Determine the best move from a list of candidate moves "possibleMoves"
/// Returns "null" if no move can be made
/// </summary>
((int x, int y) from, (int x, int y) to)? GetBestMove(int[,] state, IEnumerable<((int x, int y) from, (int x, int y) to)> possibleMoves)
{
int? bestRank = null;
@@ -164,9 +369,9 @@ IEnumerable<(int x, int y)> GetPossibleMoves(int[,] state, (int x, int y) from)
foreach (var move in possibleMoves)
{
int rank = AnalyzeMove(state, move.from, move.to);
int rank = RankMove(state, move.from, move.to);
if (rank > bestRank)
if (bestRank == null || rank > bestRank)
{
bestRank = rank;
bestMove = move;
@@ -176,6 +381,11 @@ IEnumerable<(int x, int y)> GetPossibleMoves(int[,] state, (int x, int y) from)
return bestMove;
}
/// <summary>
/// Examine the entire board and record all possible moves
/// Return the best move found, if one exists
/// Returns "null" if no move found
/// </summary>
((int x, int y) from, (int x, int y) to)? CalculateMove(int[,] state)
{
var possibleMoves = new List<((int x, int y) from, (int x, int y) to)>();
@@ -193,118 +403,86 @@ IEnumerable<(int x, int y)> GetPossibleMoves(int[,] state, (int x, int y) from)
var bestMove = GetBestMove(state, possibleMoves);
return bestMove;
}
(int x, int y) GetJumpedPiece((int x, int y) from, (int x, int y) to)
{
var midX = (to.x + from.x) / 2;
var midY = (to.y + from.y) / 2;
return (midX, midY);
}
int[,] ApplyMove(int[,] state, (int x, int y) from, (int x, int y) to)
{
state[to.x, to.y] = state[from.x, from.y];
state[from.x, from.y] = 0;
if ( (to.y == 0 && state[to.x, to.y] == -1)
||(to.y == 7 && state[to.x, to.y] == 1))
{
// make the piece a king
state[to.x, to.y] *= 2;
}
if (IsJumpMove(from, to))
{
// a jump was made
// remove the jumped piece from the board
var jump = GetJumpedPiece(from, to);
state[jump.x, jump.y] = 0;
}
return state;
}
/// <summary>
/// The logic behind the Computer's turn
/// Look for valid moves and possible subsequent moves
/// </summary>
(bool moveMade, int[,] state) ComputerTurn(int[,] state)
{
// Get best move available
var move = CalculateMove(state);
if (move == null)
{
// No move can be made
return (false, state);
}
Console.Write($"FROM {move.Value.from.x} {move.Value.from.y} ");
var from = move.Value.from;
Console.Write($"FROM {from.x} {from.y} ");
// Continue to make moves until no more valid moves can be made
while (move != null)
{
Console.WriteLine($"TO {move.Value.to.x} {move.Value.to.y}");
state = ApplyMove(state, move.Value.from, move.Value.to);
if (IsJumpMove(move.Value.from, move.Value.to))
var to = move.Value.to;
Console.WriteLine($"TO {to.x} {to.y}");
state = ApplyMove(state, from, to);
if (!IsJumpMove(from, to))
break;
// check for double / triple / etc. jump
var possibleMoves = new List<((int x, int y) from, (int x, int y) to)>();
from = to;
foreach (var candidate in GetPossibleMoves(state, from))
{
// check for double / triple / etc. jump
var possibleMoves = new List<((int x, int y) from, (int x, int y) to)>();
var from = move.Value.to;
foreach (var to in GetPossibleMoves(state, from))
if (IsJumpMove(from, candidate))
{
if (IsJumpMove(from, to))
{
possibleMoves.Add((from, to));
}
possibleMoves.Add((from, candidate));
}
move = GetBestMove(state, possibleMoves);
}
// Get best jump move
move = GetBestMove(state, possibleMoves);
}
// apply crowns to any new Kings
state = CrownKingPieces(state);
return (true, state);
}
#endregion
#region Player Logic
/// <summary>
/// Get input from the player in the form "x,y" where x and y are integers
/// If invalid input is received, return null
/// If input is valid, return the coordinate of the location
/// </summary>
(int x, int y)? GetCoordinate(string prompt)
{
Console.Write(prompt + "? ");
var input = Console.ReadLine();
var parts = input.Split(",");
if (parts.Length != 2)
// split the string into multiple parts
var parts = input?.Split(",");
if (parts?.Length != 2)
// must be exactly 2 parts
return null;
int x;
if (!int.TryParse(parts[0], out x))
// first part is not a number
return null;
int y;
if (!int.TryParse(parts[1], out y))
//second part is not a number
return null;
return (x, y);
}
bool IsValidMove(int[,] state, (int x, int y) from, (int x, int y) to)
{
if (state[to.x, to.y] != 0)
{
return false;
}
var deltaX = Math.Abs(to.x - from.x);
var deltaY = Math.Abs(to.y - from.y);
if (deltaX != 1 || deltaX != 2)
{
return false;
}
if (deltaX != deltaY)
{
return false;
}
if (state[from.x, from.y] == 1 && Math.Sign(to.y - from.y) <= 0)
{
// only kings can move downwards
return false;
}
if (deltaX == 2)
{
var jump = GetJumpedPiece(from, to);
if (state[jump.x, jump.y] >= 0)
{
// no valid piece to jump
return false;
}
}
return true;
}
int [,] PlayerTurn(int[,] state)
/// <summary>
/// Get the move from the player.
/// return a tuple of "from" and "to" representing a valid move
///
/// </summary>
((int x, int y) from, (int x,int y) to) GetPlayerMove(int[,] state)
{
// The original program has some issues regarding user input
// 1) There is minimal data sanity checks
// 1) There are minimal data sanity checks in the original:
// a) FROM piece must be owned by player
// b) TO location must be empty
// c) the FROM and TO x's must be less than 2 squares away
@@ -313,119 +491,111 @@ int [,] PlayerTurn(int[,] state)
// if the piece even moves.
// 2) Once a valid FROM is selected, a TO must be selected.
// If there are no valid TO locations, you are soft-locked
// This approach is intentionally different
// This approach is intentionally different from the original
// but maintains the original intent as much as possible
// 1) Select a FROM location
// 2) If FROM is invalid, return to step 1
// 3) Select a TO location
// 4) If TO is invalid or the implied move is invalid,
// return to step 1
(int x, int y)? from = null;
(int x, int y)? to = null;
var valid = false;
// There is still currently no way for the player to indicate that no move can be made
// This matches the original logic, but is a candidate for a refactor
do
{
from = GetCoordinate("FROM");
var from = GetCoordinate("FROM");
if ((from != null)
&& !IsOutOfBounds(from.Value)
&& (state[from.Value.x, from.Value.y] > 0))
{
to = GetCoordinate("TO");
// we have a valid "from" location
var to = GetCoordinate("TO");
if ((to != null)
&& !IsOutOfBounds(to.Value)
&& IsValidMove(state, from.Value, to.Value))
&& IsValidPlayerMove(state, from.Value, to.Value))
{
valid = true;
// we have a valid "to" location
return (from.Value, to.Value);
}
}
} while (!valid);
bool jumping = false;
} while (true);
}
/// <summary>
/// Get a subsequent jump from the player if they can / want to
/// returns a move ("from", "to") if a player jumps
/// returns null if a player does not make another move
/// The player must input negative numbers for the coordinates to indicate
/// that no more moves are to be made. This matches the original implementation
/// </summary>
((int x, int y) from, (int x, int y) to)? GetPlayerSubsequentJump(int[,] state, (int x, int y) from)
{
do
{
state = ApplyMove(state, from.Value, to.Value);
jumping = IsJumpMove(from.Value, to.Value);
if (jumping)
var to = GetCoordinate("+TO");
if ((to != null)
&& !IsOutOfBounds(to.Value)
&& IsValidPlayerMove(state, from, to.Value)
&& IsJumpMove(from, to.Value))
{
from = to;
valid = false;
do
{
to = GetCoordinate("+TO");
if ((to != null)
&& !IsOutOfBounds(to.Value)
&& IsValidMove(state, from.Value, to.Value)
&& IsJumpMove(from.Value, to.Value))
{
valid = true;
}
// we have a valid "to" location
return (from, to.Value); ;
}
if (to != null && to.Value.x < 0 && to.Value.y < 0)
{
jumping = false;
break;
}
}
while (!valid);
if (to != null && to.Value.x < 0 && to.Value.y < 0)
{
// player has indicated to not make any more moves
return null;
}
}
while (jumping);
while (true);
}
/// <summary>
/// The logic behind the Player's turn
/// Get the player input for a move
/// Get subsequent jumps, if possible
/// </summary>
int [,] PlayerTurn(int[,] state)
{
var move = GetPlayerMove(state);
do
{
state = ApplyMove(state, move.from, move.to);
if (!IsJumpMove(move.from, move.to))
{
// If player doesn't make a jump move, no further moves are possible
break;
}
var nextMove = GetPlayerSubsequentJump(state, move.to);
if (nextMove == null)
{
// another jump is not made
break;
}
move = nextMove.Value;
}
while (true);
// check to see if any kings need crowning
state = CrownKingPieces(state);
return state;
}
#endregion
bool CheckForComputerWin(int[,] state)
{
bool playerAlive = false;
foreach (var piece in state)
{
if (piece > 0)
{
playerAlive = true;
break;
}
}
return !playerAlive;
}
bool CheckForPlayerWin(int[,] state)
{
bool computerAlive = false;
foreach (var piece in state)
{
if (piece < 0)
{
computerAlive = true;
break;
}
}
return !computerAlive;
}
/*****************************************************************************
*
* Main program starts here
*
****************************************************************************/
void ComputerWins()
{
Console.WriteLine("I WIN.");
}
void PlayerWins()
{
Console.WriteLine("YOU WIN.");
}
// Main program starts here
WriteCenter("CHECKERS");
WriteCenter("CREATIVE COMPUTING MORRISTOWN, NEW JERSEY");
SkipLines(3);
Console.WriteLine("THIS IS THE GAME OF CHECKERS. THE COMPUTER IS X,");
Console.WriteLine("AND YOU ARE O. THE COMPUTER WILL MOVE FIRST.");
Console.WriteLine("SQUARES ARE REFERRED TO BY A COORDINATE SYSTEM.");
Console.WriteLine("(0,0) IS THE LOWER LEFT CORNER");
Console.WriteLine("(0,7) IS THE UPPER LEFT CORNER");
Console.WriteLine("(7,0) IS THE LOWER RIGHT CORNER");
Console.WriteLine("(7,7) IS THE UPPER RIGHT CORNER");
Console.WriteLine("THE COMPUTER WILL TYPE '+TO' WHEN YOU HAVE ANOTHER");
Console.WriteLine("JUMP. TYPE TWO NEGATIVE NUMBERS IF YOU CANNOT JUMP.");
SkipLines(3);
WriteIntroduction();
// initalize state - empty spots initialize to 0
// set player pieces to 1, computer pieces to -1
// turn your head to the right to visualize the board.
// kings will be represented by -2 (for computer) and 2 (for player)
int[,] state = new int[8, 8] {
{ 1, 0, 1, 0, 0, 0,-1, 0 },
{ 0, 1, 0, 0, 0,-1, 0,-1 },
@@ -443,9 +613,10 @@ while (true)
(moveMade, state) = ComputerTurn(state);
if (!moveMade)
{
// in the original program the computer wins if it cannot make a move
// I believe the player should win in this case, assuming the player can make a move
// In the original program the computer wins if it cannot make a move
// I believe the player should win in this case, assuming the player can make a move.
// if neither player can make a move, the game should be draw.
// I have left it as the original logic for now.
ComputerWins();
break;
}