tictactoe: hard ai uses chance to win in diagonal

src/main/java/de/tims/tictactoe/ai/AIHard.java

@@ -21,6 +21,7 @@ public class AIHard implements TicTacToeAI {
 	public void calculateNextMove() {
 		int ownCharsInRow = 0;
 		int ownCharsInCol = 0;
+		int ownCharsInDiag = 0;
 		int charsOfOpponentInRow = 0;
 		int charsOfOpponentInCol = 0;
 		int charsOfOpponentInDiag = 0;
@@ -32,14 +33,27 @@ public class AIHard implements TicTacToeAI {
 			charsOfOpponentInRow = countCharsInRow(i, PLAYER_CHAR);
 			charsOfOpponentInCol = countCharsInCol(i, PLAYER_CHAR);
 			if (i < 2) {
+				ownCharsInDiag = countCharsInDiag(i, AI_CHAR);
 				charsOfOpponentInDiag = countCharsInDiag(i, PLAYER_CHAR);
 			}
 			
 			if (ownCharsInRow == BOARD_SIZE - 1 || ownCharsInCol == BOARD_SIZE - 1) {
 				for (int j = 0; j < BOARD_SIZE; j++) {
-					if (board[(ownCharsInRow == BOARD_SIZE - 1) ? i : j][(ownCharsInRow == BOARD_SIZE - 1) ? j : i] == EMPTY_CHAR) {
-						gl.setField((ownCharsInRow == BOARD_SIZE - 1) ? i : j, (ownCharsInRow == BOARD_SIZE - 1) ? j : i, AI_CHAR);
-						return;
+					if (ownCharsInRow == BOARD_SIZE - 1) {						
+						if (board[i][j] == EMPTY_CHAR) {
+							gl.setField(i, j, AI_CHAR);
+							return;
+						}
+					} else if (ownCharsInCol == BOARD_SIZE - 1) {
+						if (board[j][i] == EMPTY_CHAR) {
+							gl.setField(j, i, AI_CHAR);
+							return;
+						}
+					} else if (ownCharsInDiag == BOARD_SIZE - 1) {
+						if (board[j][(i == 1) ? i : BOARD_SIZE - 1 - j] == EMPTY_CHAR) {
+							gl.setField(j, (i == 1) ? j : BOARD_SIZE - 1 - j, AI_CHAR);
+							return;
+						}
 					}
 				}
 			}

src/test/java/de/tims/tictactoe/ai/AIHardTest.java

@@ -121,6 +121,17 @@ class AIHardTest {
 		verify(gl, times(1)).setField(1, 0, realChar);
 	}
 	
+	@Test
+	void when2inDiagSetThird() {
+		char realChar = 'o';
+		doReturn(new char[][] { {'o', '-', 'x'}, {'-', 'o', 'x'}, {'-', '-', '-'} }).when(gl).getBoard();
+		
+		TicTacToeAI ai = new AIHard(gl);
+		ai.calculateNextMove();
+		
+		verify(gl, times(1)).setField(2, 2, realChar);
+	}
+	
 	@ParameterizedTest
 	@MethodSource("testCasesForCountCharsInRow")
 	void countCharsInRowTest(String testName, char[][] board, int rowNum, char charToCount, int expectedResult) {