2020-01-04 13:13:13 +01:00
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using System;
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using System.Text;
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namespace TicTacToe {
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2020-01-04 11:54:13 +01:00
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public class Grid {
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2020-01-04 13:13:13 +01:00
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public const int GRIDSIZE = 3;
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private const Player GameBeginner = Player.Cross;
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private Player NextGameBeginner = GameBeginner;
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private readonly Player[,] _field = new Player[GRIDSIZE, GRIDSIZE];
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private Player? winner;
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private ((int x, int y) p1, (int x, int y) p2)? winningLine;
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public event EventHandler<Player> ExpectNextTurn;
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public event EventHandler<Player> GameOver;
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public Player this[int x, int y] { get => _field[x, y]; }
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public bool IsGameOver { get; private set; } = false;
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public Player ActivePlayer { get; private set; } = GameBeginner;
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public Player Winner { get => winner.Value; private set => winner = value; }
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public ((int x, int y) p1, (int x, int y) p2) WinningLine { get => winningLine.Value; private set => winningLine = value; }
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public Grid() {
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Reset();
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}
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/// <summary>
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/// Checks if a given field is empty.
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/// </summary>
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/// <param name="x">Column index</param>
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/// <param name="y">Row index</param>
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/// <returns>True if the field is empty</returns>
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public bool IsEmpty(int x, int y) => _field[x, y] == Player.Empty;
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public void Reset() {
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ActivePlayer = NextGameBeginner;
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NextGameBeginner = EnemyOf(NextGameBeginner);
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IsGameOver = false;
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winner = null;
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winningLine = null;
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for (var y = 0; y < GRIDSIZE; y++)
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for (var x = 0; x < GRIDSIZE; x++)
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_field[x, y] = Player.Empty;
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ExpectNextTurn?.Invoke(this, ActivePlayer);
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}
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/// <summary>
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/// Checks if a given field is not empty.
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/// </summary>
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/// <param name="x">Column index</param>
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/// <param name="y">Row index</param>
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/// <returns>True if the field is set</returns>
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public bool IsSet(int x, int y) => _field[x, y] != Player.Empty;
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public void PickSpot(int x, int y) {
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if (IsGameOver)
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throw new InvalidOperationException("Cannot pick spot on finished game!");
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if (!IsEmpty(x, y))
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throw new InvalidOperationException("Cannot pick already picked spot!");
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_field[x, y] = ActivePlayer;
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TurnOver();
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if (!IsGameOver)
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ExpectNextTurn?.Invoke(this, ActivePlayer);
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}
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/// <summary>
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/// Tests if the game is over and updates the properties.
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/// </summary>
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/// <see cref="IsGameOver"/>
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/// <see cref="Winner"/>
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private void TurnOver() {
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if (CheckRows() ||
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CheckColumns() ||
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CheckDiagonalPrimary() ||
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CheckDiagonalSecondary() ||
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CheckDraw()) { // Important to check after all other cases as there might be a full field with a winner
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IsGameOver = true;
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GameOver?.Invoke(this, Winner);
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} else {
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IsGameOver = false;
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ActivePlayer = EnemyOf(ActivePlayer);
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}
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}
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private static Player EnemyOf(Player player) {
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switch (player) {
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case Player.Cross:
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return Player.Circle;
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case Player.Circle:
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return Player.Cross;
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default:
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throw new Exception("Unexpected enumerable state!");
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}
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}
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#region GameOverTests
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/// <summary>
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/// Checks if a field is full and there is no winner
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/// </summary>
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/// <returns></returns>
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private bool CheckDraw() {
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for (var y = 0; y < GRIDSIZE; y++) {
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for (var x = 0; x < GRIDSIZE; x++) {
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if (IsEmpty(x, y))
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2020-01-04 11:54:13 +01:00
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return false;
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2020-01-04 13:13:13 +01:00
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}
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}
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Winner = Player.Empty;
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2020-01-04 11:54:13 +01:00
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return true;
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}
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2020-01-04 13:13:13 +01:00
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/// <summary>
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/// Checks primary diagonal on a win.
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/// </summary>
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/// <returns>True if a win was found</returns>
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private bool CheckDiagonalPrimary() {
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var circlecount = 0;
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var crosscount = 0;
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for (var x = 0; x < GRIDSIZE; x++) {
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switch (_field[x, x]) {
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case Player.Circle:
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circlecount++;
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break;
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case Player.Cross:
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crosscount++;
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break;
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case Player.Empty:
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return false;
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default:
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throw new InvalidProgramException("Unexpected enumerable state!");
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}
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}
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if (crosscount == GRIDSIZE) {
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Winner = Player.Cross;
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WinningLine = ((0, 0), (GRIDSIZE, GRIDSIZE));
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return true;
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}
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if (circlecount == GRIDSIZE) {
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Winner = Player.Circle;
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WinningLine = ((0, 0), (GRIDSIZE, GRIDSIZE));
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return true;
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}
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return false;
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}
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/// <summary>
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/// Checks secondary diagonal on a win.
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/// </summary>
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/// <returns>True if a win was found</returns>
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private bool CheckDiagonalSecondary() {
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var circlecount = 0;
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var crosscount = 0;
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for (var x = 0; x < GRIDSIZE; x++) {
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switch (_field[x, GRIDSIZE - 1 - x]) {
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case Player.Circle:
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circlecount++;
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break;
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case Player.Cross:
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crosscount++;
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break;
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case Player.Empty:
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return false;
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default:
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throw new InvalidProgramException("Unexpected enumerable state!");
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}
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}
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if (crosscount == GRIDSIZE) {
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Winner = Player.Cross;
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WinningLine = ((0, GRIDSIZE), (GRIDSIZE, 0));
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return true;
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}
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if (circlecount == GRIDSIZE) {
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Winner = Player.Circle;
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WinningLine = ((0, GRIDSIZE), (GRIDSIZE, 0));
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return true;
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}
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return false;
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}
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2020-01-04 11:54:13 +01:00
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2020-01-04 13:13:13 +01:00
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/// <summary>
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/// Checks all columns on a win.
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/// </summary>
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/// <returns>True if a win was found</returns>
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private bool CheckColumns() {
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for (var x = 0; x < GRIDSIZE; x++) {
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if (CheckColumn(in x)) {
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WinningLine = ((x, 0), (x, GRIDSIZE));
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return true;
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}
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}
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return false;
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2020-01-04 11:54:13 +01:00
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}
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2020-01-04 13:13:13 +01:00
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/// <summary>
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/// Checks a specific column on a win.
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/// </summary>
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/// <param name="y">Column index</param>
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/// <returns>True if a win was found</returns>
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private bool CheckColumn(in int y) {
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var circlecount = 0;
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var crosscount = 0;
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for (var x = 0; x < GRIDSIZE; x++) {
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switch (_field[y, x]) {
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case Player.Circle:
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circlecount++;
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break;
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case Player.Cross:
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crosscount++;
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break;
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case Player.Empty:
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return false;
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default:
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throw new InvalidProgramException("Unexpected enumerable state!");
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}
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}
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if (crosscount == GRIDSIZE) {
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Winner = Player.Cross;
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return true;
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}
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if (circlecount == GRIDSIZE) {
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Winner = Player.Circle;
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return true;
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}
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return false;
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}
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/// <summary>
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/// Checks all rows on a win.
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/// </summary>
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/// <returns>True if a win was found</returns>
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private bool CheckRows() {
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for (var y = 0; y < GRIDSIZE; y++) {
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if (CheckRow(in y)) {
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WinningLine = ((0, y), (GRIDSIZE, y));
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return true;
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}
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}
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return false;
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}
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/// <summary>
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/// Checks a specific row on a win.
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/// </summary>
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/// <param name="y">Row index</param>
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/// <returns>True if a win was found</returns>
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private bool CheckRow(in int y) {
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var circlecount = 0;
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var crosscount = 0;
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for (var x = 0; x < GRIDSIZE; x++) {
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switch (_field[x, y]) {
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case Player.Circle:
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circlecount++;
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break;
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case Player.Cross:
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crosscount++;
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break;
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case Player.Empty:
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return false;
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default:
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throw new InvalidProgramException("Unexpected enumerable state!");
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}
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}
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if (crosscount == GRIDSIZE) {
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Winner = Player.Cross;
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return true;
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}
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if (circlecount == GRIDSIZE) {
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Winner = Player.Circle;
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return true;
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}
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return false;
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}
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#endregion
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/// <summary>
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/// Writes the grid data into a string. All rows are printed pipe ('|') separated and all row items are printed comma (',') separated.
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/// </summary>
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/// <returns>A string uniquely identifying the grid</returns>
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public override string ToString() {
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var sb = new StringBuilder();
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for (var y = 0; y < GRIDSIZE; y++) {
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if (y > 0)
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sb.Append("|");
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for (var x = 0; x < GRIDSIZE; x++) {
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if (x > 0)
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sb.Append(",");
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sb.Append(GetPlayerChar(_field[x, y]));
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}
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}
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return sb.ToString();
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2020-01-04 11:54:13 +01:00
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}
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2020-01-04 13:13:13 +01:00
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public static char GetPlayerChar(Player player) {
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switch (player) {
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case Player.Empty:
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return ' ';
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case Player.Cross:
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return 'X';
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case Player.Circle:
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return 'O';
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default:
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throw new Exception("Unexpected enumerable state!");
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};
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2020-01-04 11:54:13 +01:00
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}
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}
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}
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