Create Tic tac toe

Tic tac toe

@@ -0,0 +1,172 @@
+#include <iostream>
+#include <cstring>
+#include <algorithm>
+#include <ctime>
+
+using namespace std;
+
+#define compareBoxes(box1, box2, box3) ((board[box1] == board[box2]) && (board[box2] == board[box3]) && (board[box1] != 0)) //Checkes if three items are the same, and makes sure they're not 0's.
+#define numberToLetter(x) ((x > 0) ? (x == 1) ? 'X' : 'O' : ' ') //Takes the number and turns it into the letter or space.
+
+int getWinner(int board[9]) {
+	//Finds winner of game, if there is no winner, returns 0.
+	int winner = 0;
+	for (int x = 0; x < 3; x++) {
+		if (compareBoxes(3*x, 3*x+1, 3*x+2)) { //Chekcs rows.
+			winner = board[3*x];
+			break;
+		} else if (compareBoxes(x, x+3, x+6)) { //Checks columns.
+			winner = board[x];
+			break;
+
+		} else if (compareBoxes(2*x, 4, 8-2*x) && (x < 2)) { //Checks diagonals. Doesn't check if x == 2.
+			winner = board[4];
+			break;
+		}
+	}
+	return winner;
+}
+bool gameOver(int board[9]){
+	//Checks if game is over, and announces who won, or if it was a tie.
+	int winner = getWinner(board);
+	if (winner > 0) {
+		cout << numberToLetter(winner) << " wins!"<< endl;
+		return true;
+	} 
+	for (int x = 0; x < 9; x++) {
+		if (board[x] == 0) return false;
+	}
+	cout << "Tie!\n\n";
+	return true;
+}
+
+int willWin(int board[9], int player) {
+	//Checks if a given player could win in the next plank.
+	for (int x = 0; x < 9; x++) {
+		int tempBoard[9];
+		memcpy(tempBoard, board, 36);
+		if (board[x] > 0) continue;
+		tempBoard[x] = player;
+		if(getWinner(tempBoard) == player) return x;
+	}
+	return -1;
+}
+
+int exceptionalCase(int board[9]) {
+	//Finds bords that are exceptions to how the algorithm works.
+	int cases[2][9] = {{1,0,0,0,2,0,0,0,1}, {0,1,0,1,2,0,0,0,0}}; //Boards that don't work with algorithm.
+	int answers[2][4] = {{3,3,3,3}, {2,8,6,0}};
+	int rotatedBoard[9] = {6,3,0,7,4,1,8,5,2};
+	int newBoard[9];
+	int tempBoard[9];
+	for(int x = 0; x < 9; x++) {
+		newBoard[x] = board[x];
+	}
+	for (int caseIndex = 0; caseIndex < 2; caseIndex++) {
+		for(int rotation = 0; rotation < 4; rotation++) {
+			for (int x = 0; x < 9; x++) 
+				tempBoard[x] = newBoard[x];
+
+			int match = 0;
+			//Rotates board so it works with different versions of the same board.
+			for (int box = 0; box < 9; box++) {
+				newBoard[box] = tempBoard[rotatedBoard[box]];
+			}
+
+			for (int x = 0; x < 9; x++) {
+				if (newBoard[x] == cases[caseIndex][x]) match++;
+				else break;
+			}
+			if (match == 9) return answers[caseIndex][rotation];
+		}
+	}
+	return -1;
+}
+
+int getSpace(int board[9], int spaces[4]) {
+	//Gets a random corner or side that's not taken.
+	bool isSpaceEmpty = false;
+	int y;
+	for (int x = 0; x < 4; x++) {
+		if (board[spaces[x]] == 0) {
+			isSpaceEmpty = true;
+			break;
+		}
+	}
+	if (isSpaceEmpty) {
+		do {
+			y = rand() % 4;
+		} while (board[spaces[y]] != 0);
+		return spaces[y];
+	}
+	return -1;
+}
+
+void outputBoard(int board[9]) {
+	for(int line = 0; line < 3; line++){
+		for (int box = 0; box < 3; box++) {
+			cout << numberToLetter(board[3*line+box]) << ((box < 2) ? '|' : '\n');
+		}
+		cout << ((line < 2) ? "-----\n" : "\n");
+	}
+}
+
+int main(){
+	int board[9] = {0,0,0,0,0,0,0,0,0}; //Starts empty board.
+	int possibleWinner;
+	int move;
+	bool isInvalid;
+	string moveString;
+	srand((int) time(0));
+	int corners[4] = {0,2,6,8};
+	int sides[4] = {1,3,5,7};
+
+	cout << "1|2|3\n-----\n4|5|6\n-----\n7|8|9\n\n";
+
+	while (true) {
+		//Player X decides what move they'll do.
+		do {
+			cout << "X: ";
+			getline(cin, moveString);
+			move = moveString[0] - '1';
+			if (move > 8 || move < 0 || board[move] != 0) {
+				cout << "Invalid input" << endl;
+				isInvalid = true;
+			} else {
+				board[move] = 1;
+				isInvalid = false;
+				cout << endl;
+			}
+		} while (isInvalid);
+
+		//Decides whether or not the game continues.
+		if (gameOver(board) > 0) {
+			outputBoard(board);
+			break;
+		}
+
+		//Player O decides which move they'll do.
+		bool good = false;
+		for (int x = 2; x > 0; x--){
+			possibleWinner = willWin(board, x);
+			if (possibleWinner != -1) {
+				board[possibleWinner] = 2;
+				good = true;
+				break;
+			}
+		}
+		if (good);
+		else if (board[4] == 0) board[4] = 2; //Middle.
+		else if (exceptionalCase(board) > -1) board[exceptionalCase(board)] = 2; //Exception boards.
+		else if (getSpace(board, corners) != -1) board[getSpace(board, corners)] = 2; //Corners
+		else board[getSpace(board, sides)] = 2; //Sides
+
+		//Prints the board to the screen.
+		outputBoard(board);
+
+		//Decides whether or not the game continues.
+		if(gameOver(board)) break;
+
+	}
+	return 0;
+}