feat: detect other diagonal wins for lower win piece counts

.gitignore

@@ -1,3 +1,6 @@
+lib/Minimax.md
+lib/ProjectExplanation.md
+
 # Logs
 logs
 *.log

lib/TicTacToe.js

@@ -20,6 +20,10 @@ function randomInteger(min, max) {
   return Math.round(Math.random() * (max - min) + min);
 }
 
+function intSum(min, max) {
+  return ((max - min) + 1) * (min + max) / 2;
+}
+
 /** A single thread, blocking, **tic-tac-toe** class game representation that
  * can use the **`minimax`** algorithm to search for the best possible move.
  */
@@ -231,34 +235,72 @@ class TicTacToe {
     }
 
     // check diag \
-    let samePieceSecondLastDiag = 1;
-    for (let i = 0; i < this.grid - 1; ++i) {
-      if (
-        this.board[i * this.grid + i] === this.board[(i + 1) * this.grid + (i + 1)] &&
-        this.board[i * this.grid + i] !== NA
-      ) {
-        samePieceSecondLastDiag++;
-        if (samePieceSecondLastDiag === this.pieceWinCount) {
-          this.winner = this.board[i * this.grid + i];
-          return this.board[i * this.grid + i];
+    for (let i = 0; i < this.grid; ++i) {
+      let samePiece = 1, prevPiece = null;
+      for (let j = 0; j < i + 1; ++j) {
+        const CURRENT_INDEX = (this.grid - i) + ((this.grid + 1) * j) - 1;
+        if (prevPiece === this.board[CURRENT_INDEX] && this.board[CURRENT_INDEX] !== NA) {
+          samePiece++;
+          if (samePiece === this.pieceWinCount) {
+            this.winner = this.board[CURRENT_INDEX];
+            return this.board[CURRENT_INDEX];
+          }
+        } else {
+          samePiece = 1;
         }
-      } else {
-        samePieceSecondLastDiag = 1;
+        prevPiece = this.board[CURRENT_INDEX];
+      }
+    }
+
+    for (let i = 1; i < this.grid; ++i) {
+      let samePiece = 1, prevPiece = null;
+      for (let j = 0; this.grid - i - j > 0; ++j) {
+        const CURRENT_INDEX = (i * this.grid) + ((this.grid + 1) * j);
+        if (prevPiece === this.board[CURRENT_INDEX] && this.board[CURRENT_INDEX] !== NA) {
+          samePiece++;
+          if (samePiece === this.pieceWinCount) {
+            this.winner = this.board[CURRENT_INDEX];
+            return this.board[CURRENT_INDEX];
+          }
+        } else {
+          samePiece = 1;
+        }
+        prevPiece = this.board[CURRENT_INDEX];
       }
     }
 
     // check diag /
-    const diagStep = this.grid - 1;
-    let samePieceLastDiag = 1;
+    for (let i = 0; i < this.grid; ++i) {
+      let samePiece = 1, prevPiece = null;
+      for (let j = 0; j < i + 1; ++j) {
+        const CURRENT_INDEX = i + (j * this.grid) - j;
+        if (prevPiece === this.board[CURRENT_INDEX] && this.board[CURRENT_INDEX] !== NA) {
+          samePiece++;
+          if (samePiece === this.pieceWinCount) {
+            this.winner = this.board[CURRENT_INDEX];
+            return this.board[CURRENT_INDEX];
+          }
+        } else {
+          samePiece = 1;
+        }
+        prevPiece = this.board[CURRENT_INDEX];
+      }
+    }
+
     for (let i = 1; i < this.grid; ++i) {
-      if (this.board[i * diagStep] === this.board[(i + 1) * diagStep] && this.board[i * diagStep] !== NA) {
-        samePieceLastDiag++;
-        if (samePieceLastDiag === this.pieceWinCount) {
-          this.winner = this.board[i * diagStep];
-          return this.board[i * diagStep];
+      let samePiece = 1, prevPiece = null;
+      for (let j = 0; this.grid - i - j > 0; ++j) {
+        const CURRENT_INDEX = ((this.grid * (i + 1)) - 1) + ((this.grid - 1) * j);
+        if (prevPiece === this.board[CURRENT_INDEX] && this.board[CURRENT_INDEX] !== NA) {
+          samePiece++;
+          if (samePiece === this.pieceWinCount) {
+            this.winner = this.board[CURRENT_INDEX];
+            return this.board[CURRENT_INDEX];
+          }
+        } else {
+          samePiece = 1;
         }
-      } else {
-        samePieceLastDiag = 1;
+        prevPiece = this.board[CURRENT_INDEX];
       }
     }
 

tests.js

@@ -1,8 +1,63 @@
 import { TicTacToe, NA, P1, P2 } from './lib/TicTacToe.js';
 
 const t = new TicTacToe({ gridLength: 3 });
+const fbf = new TicTacToe({ gridLength: 4, winCount: 3 });
 let failedTests = 0;
 
+const fbfWinners = [NA, P1, P2, P1, P2, P1, P2, P1, P2];
+const fbfBoardStates = [
+  [
+    P2, NA, NA, P2,
+    NA, P1, NA, NA,
+    NA, NA, P2, NA,
+    P1, NA, NA, P1
+  ],
+  [
+    NA, NA, P1, NA,
+    NA, P1, NA, NA,
+    P1, NA, NA, NA,
+    NA, NA, NA, NA
+  ],[
+    NA, NA, NA, NA,
+    NA, NA, NA, P2,
+    NA, NA, P2, NA,
+    NA, P2, NA, NA
+  ],[
+    NA, P1, NA, NA,
+    NA, NA, P1, NA,
+    NA, NA, NA, P1,
+    NA, NA, NA, NA
+  ],[
+    NA, NA, NA, NA,
+    P2, NA, NA, NA,
+    NA, P2, NA, NA,
+    NA, NA, P2, NA
+  ],[
+    NA, NA, NA, NA,
+    NA, NA, P1, NA,
+    NA, P1, NA, NA,
+    P1, NA, NA, NA
+  ],[
+    NA, NA, NA, NA,
+    NA, P2, NA, NA,
+    NA, NA, P2, NA,
+    NA, NA, NA, P2
+  ],[
+    NA, NA, NA, P1,
+    NA, NA, P1, NA,
+    NA, P1, NA, NA,
+    NA, NA, NA, NA
+  ],[
+    P2, NA, NA, NA,
+    NA, P2, NA, NA,
+    NA, NA, P2, NA,
+    NA, NA, NA, NA
+  ],
+];
+
+console.log('============ 4x4 - piece 3 win state tests ============ ');
+failedTests += fbf.testEvaluation(fbfBoardStates, fbfWinners);
+
 const winners = [NA, P1, P1, P1, P1, P1, P1, P2, P2, P2, P2, P2, P2, P1, P1, P2, P2, NA];
 
 const winBoardStates = [
@@ -26,6 +81,7 @@ const winBoardStates = [
   [P2, P1, P2, P1, P2, NA, NA, P1, NA], // no winner
 ];
 
+console.log('============ 3x3 win state tests ============ ');
 failedTests += t.testEvaluation(winBoardStates, winners);
 
 const correctMoves = [
@@ -86,6 +142,7 @@ const moveBoardStates = [
   [P1, NA, P1, P2, NA, P2, P1, P2, P1],
 ];
 
+console.log('============ 3x3 move generation test ============ ');
 failedTests += t.testGenerateMoves(moveBoardStates, correctMoves);
 
 if (failedTests > 0) {