LeetCode – Arrays – Winner in Tic Tac Toe

Tic-tac-toe is played by two players A and B on a 3 x 3 grid.

Here are the rules of Tic-Tac-Toe:

• Players take turns placing characters into empty squares (” “).
• The first player A always places “X” characters, while the second player B always places “O” characters.
• “X” and “O” characters are always placed into empty squares, never on filled ones.
• The game ends when there are 3 of the same (non-empty) character filling any row, column, or diagonal.
• The game also ends if all squares are non-empty.
• No more moves can be played if the game is over.

Given an array moves where each element is another array of size 2 corresponding to the row and column of the grid where they mark their respective character in the order in which A and B play.

Return the winner of the game if it exists (A or B), in case the game ends in a draw return “Draw”, if there are still movements to play return “Pending”.

You can assume that moves is valid (It follows the rules of Tic-Tac-Toe), the grid is initially empty and A will play first.

Example 1:

Input: moves = [[0,0],[2,0],[1,1],[2,1],[2,2]]
Output: "A"
Explanation: "A" wins, he always plays first.
"X  "    "X  "    "X  "    "X  "    "X  "
"   " -> "   " -> " X " -> " X " -> " X "
"   "    "O  "    "O  "    "OO "    "OOX"

Example 2:

Input: moves = [[0,0],[1,1],[0,1],[0,2],[1,0],[2,0]]
Output: "B"
Explanation: "B" wins.
"X  "    "X  "    "XX "    "XXO"    "XXO"    "XXO"
"   " -> " O " -> " O " -> " O " -> "XO " -> "XO " 
"   "    "   "    "   "    "   "    "   "    "O  "

class Solution {
    public String tictactoe(int[][] moves) {
        String[][] ab_moves = new String[3][3];
        int acounter = 0;
        int bcounter = 0;
        String result = null;
        for(int i=0;i<moves.length;i++){
            int row = moves[i][0];
            int col = moves[i][1];
            
            if(i%2 == 0){
              acounter++;
              ab_moves[row][col] = "A";
              if(acounter >= 3) result = validateGame(ab_moves,row,col,"A");
            } 
            else{
              bcounter++;
              ab_moves[row][col] = "B";
              if(bcounter >= 3) result = validateGame(ab_moves,row,col,"B");
            }
            if(result != null) return result;
        }
        if(result == null && moves.length == 9) result = "Draw";
        else result = "Pending";
        
        return result;
    }
    
    public String validateGame(String[][] ab_moves, int row, int col, String identifier){
        String result = null;
        if((row == 0 && col == 0) || (row == 2 && col == 0) || (row == 0 && col == 2) || (row == 2 && col == 2) || (row ==1 && col == 1)){
                if(identifier.equals(ab_moves[0][0]) && identifier.equals(ab_moves[1][1]) && identifier.equals(ab_moves[2][2])) result = identifier;
                else if(identifier.equals(ab_moves[0][2]) && identifier.equals(ab_moves[1][1]) && identifier.equals(ab_moves[2][0])) result = identifier;
                else result = null;
        }
        if(result == null){
            for(int i=0;i<3;i++){
                if(identifier.equals(ab_moves[row][i])) result = identifier;
                else{
                    result = null;
                    break;
                }
            }
            if(result == null){
                for(int i=0;i<3;i++){
                    if(identifier.equals(ab_moves[i][col])) result = identifier;
                    else{
                        result = null;
                        break;
                    }
                }
            }
        }
        return result;
    }
}