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Fix segmentation fault in TicTacToe minimax due to incorrect board state handling #195

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Fix segmentation fault in TicTacToe minimax due to incorrect board state handling #195

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20 changes: 10 additions & 10 deletions solutions/cpp/tictactoe/Game.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -108,7 +108,7 @@ std::pair<int, int> Game::findBestMove() const {
Board tempBoard = board; // Create a copy
tempBoard.makeMove(i, j, player2->getSymbol());

int score = minimax(false, 0);
int score = minimax(tempBoard, false, 0); //pass the temporary boardState
if (score > bestScore) {
bestScore = score;
bestMove = {i, j};
Expand All @@ -120,20 +120,20 @@ std::pair<int, int> Game::findBestMove() const {
return bestMove;
}

int Game::minimax(bool isMax, int depth) const {
if (board.checkWin(player2->getSymbol())) return 10 - depth;
if (board.checkWin(player1->getSymbol())) return depth - 10;
if (board.isFull()) return 0;
int Game::minimax(Board boardState, bool isMax, int depth) const {
if (boardState.checkWin(player2->getSymbol())) return 10 - depth;
if (boardState.checkWin(player1->getSymbol())) return depth - 10;
if (boardState.isFull()) return 0;

int bestScore = isMax ? std::numeric_limits<int>::min() : std::numeric_limits<int>::max();

for (int i = 0; i < board.getSize(); i++) {
for (int j = 0; j < board.getSize(); j++) {
if (board.isEmpty(i, j)) {
Board tempBoard = board; // Create a copy
for (int i = 0; i < boardState.getSize(); i++) {
for (int j = 0; j < boardState.getSize(); j++) {
if (boardState.isEmpty(i, j)) {
Board tempBoard = boardState; // Create a copy
tempBoard.makeMove(i, j, isMax ? player2->getSymbol() : player1->getSymbol());

int score = minimax(!isMax, depth + 1);
int score = minimax(tempBoard, !isMax, depth + 1); // pass the temporary boardState recursively
bestScore = isMax ? std::max(score, bestScore) : std::min(score, bestScore);
}
}
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2 changes: 1 addition & 1 deletion solutions/cpp/tictactoe/Game.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ class Game {
private:
void computerMove();
std::pair<int, int> findBestMove() const;
int minimax(bool isMax, int depth) const;
int minimax(Board boardState, bool isMax, int depth) const; // pass the board state
};

#endif