133 lines
3.3 KiB
FSharp
133 lines
3.3 KiB
FSharp
type Brick =
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| Empty
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| Computer
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| User
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let brickToString = function
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| Empty -> ' '
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| Computer -> 'X'
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| User -> 'O'
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// y -> x -> Brick
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type Board = Map<int, Map<int, Brick> >
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let emptyBoard =
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let emptyRow = Map.ofList [0,Empty; 1,Empty; 2,Empty]
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Map.ofList [0,emptyRow; 1,emptyRow; 2,emptyRow]
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let get (b:Board) (x,y) = b.[y].[x]
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let set player (b:Board) (x,y) : Board =
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let row = b.[y].Add(x, player)
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b.Add(y, row)
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let winningPositions =
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[for x in [0..2] -> x,x] // first diagonal
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::[for x in [0..2] -> 2-x,x] // second diagonal
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::[for y in [0..2] do
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yield! [[for x in [0..2]->(y,x)]; // columns
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[for x in [0..2] -> (x,y)]]] // rows
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let hasWon player board =
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List.exists
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(fun ps -> List.forall (fun pos -> get board pos = player) ps)
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winningPositions
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let freeSpace board =
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[for x in 0..2 do
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for y in 0..2 do
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if get board (x,y) = Empty then yield x,y]
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type Evaluation =
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| Win
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| Draw
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| Lose
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let rec evaluate board move =
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let b2 = set Computer board move
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if hasWon Computer b2 then Win
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else
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match freeSpace b2 with
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| [] -> Draw
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| userChoices ->
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let b3s = List.map (set User b2) userChoices
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if List.exists (hasWon User) b3s then Lose
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elif List.exists (fun b3 -> bestOutcome b3 = Lose) b3s
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then Lose
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elif List.exists (fun b3 -> bestOutcome b3 = Draw) b3s
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then Draw
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else Win
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and findBestChoice b =
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match freeSpace b with
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| [] -> ((-1,-1), Draw)
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| choices ->
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match List.tryFind (fun c -> evaluate b c = Win) choices with
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| Some c -> (c, Win)
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| None -> match List.tryFind (fun c -> evaluate b c = Draw) choices with
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| Some c -> (c, Draw)
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| None -> (List.head choices, Lose)
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and bestOutcome b = snd (findBestChoice b)
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let bestChoice b = fst (findBestChoice b)
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let computerPlay b = set Computer b (bestChoice b)
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let printBoard b =
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printfn " | A | B | C |"
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printfn "---+---+---+---+"
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for y in 0..2 do
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printfn " %d | %c | %c | %c |"
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(3-y)
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(get b (0,y) |> brickToString)
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(get b (1,y) |> brickToString)
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(get b (2,y) |> brickToString)
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printfn "---+---+---+---+"
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let rec userPlay b =
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printfn "Which field do you play? (format: a1)"
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let input = System.Console.ReadLine()
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if input.Length <> 2
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|| input.[0] < 'a' || input.[0] > 'c'
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|| input.[1] < '1' || input.[1] > '3' then
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printfn "illegal input"
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userPlay b
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else
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let x = int(input.[0]) - int('a')
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let y = 2 - int(input.[1]) + int('1')
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if get b (x,y) <> Empty then
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printfn "Field is not free."
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userPlay b
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else
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set User b (x,y)
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let rec gameLoop b player =
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if freeSpace b = [] then
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printfn "Game over. Draw."
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elif player = Computer then
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printfn "Computer plays..."
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let b2 = computerPlay b
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printBoard b2
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if hasWon Computer b2 then
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printfn "Game over. I have won."
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else
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gameLoop b2 User
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elif player = User then
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let b2 = userPlay b
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printBoard b2
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if hasWon User b2 then
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printfn "Game over. You have won."
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else
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gameLoop b2 Computer
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// randomly choose an element of a list
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let choose =
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let rnd = new System.Random()
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fun (xs:_ list) -> xs.[rnd.Next(xs.Length)]
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// play first brick randomly
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printfn "Computer starts."
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let b = set Computer emptyBoard (choose (freeSpace emptyBoard))
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printBoard b
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gameLoop b User
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