Create 20_tic_tac_toe_winner.cpp

Author: FazeelUsmani

09 September Challenge 2021/20_tic_tac_toe_winner.cpp

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+class Solution {
+private:
+
+ // Initialize the board, n = 3 in this problem.
+ int n = 3;
+ vector<vector<int>> board;
+
+public:
+ string tictactoe(vector<vector<int>>& moves) { 
+ board.assign(n, vector<int>(n, 0));
+ int player = 1;
+
+ // For each move
+ for (vector<int> move : moves) {
+ int row = move[0];
+ int col = move[1];
+
+ // Mark the current move with the current playrer's id.
+ board[row][col] = player;
+
+ // If any of the winning conditions is met, return the current player's id.
+ if (checkRow(row, player) || checkCol(col, player) || 
+ (row == col && checkDiagonal(player)) ||
+ (row + col == n - 1 && checkAntiDiagonal(player))) {
+ return player == 1 ? "A" : "B";
+ return player == 1 ? "A" : "B";
+ }
+
+ // If no one wins so far, change to the other player alternatively. 
+ // That is from 1 to -1, from -1 to 1.
+ player *= -1;
+ }
+
+ // If all moves are completed and there is still no result, we shall check if 
+ // the grid is full or not. If so, the game ends with draw, otherwise pending.
+ return moves.size() == 3 * 3 ? "Draw" : "Pending";
+ }
+ 
+ // Check if any of 4 winning conditions to see if the current player has won.
+ bool checkRow(int row, int player) {
+ for (int col = 0; col < n; ++col) {
+ if (board[row][col] != player) return false;
+ }
+ return true;
+ }
+ 
+ bool checkCol(int col, int player) {
+ for (int row = 0; row < n; ++row) {
+ if (board[row][col] != player) return false;
+ }
+ return true;
+ }
+ 
+ bool checkDiagonal(int player) {
+ for (int row = 0; row < n; ++row) {
+ if (board[row][row] != player) return false;
+ }
+ return true;
+ }
+ 
+ bool checkAntiDiagonal(int player) {
+ for (int row = 0; row < n; ++row) {
+ if (board[row][n - 1 - row] != player) return false;
+ }
+ return true;
+ }
+};