1275. Find Winner on a Tic Tac Toe Game

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  "

Example 3:

Input: moves = [[0,0],[1,1],[2,0],[1,0],[1,2],[2,1],[0,1],[0,2],[2,2]]
Output: "Draw"
Explanation: The game ends in a draw since there are no moves to make.
"XXO"
"OOX"
"XOX"

Example 4:

Input: moves = [[0,0],[1,1]]
Output: "Pending"
Explanation: The game has not finished yet.
"X  "
" O "
"   "

 

Constraints:

  • 1 <= moves.length <= 9
  • moves[i].length == 2
  • 0 <= moves[i][j] <= 2
  • There are no repeated elements on moves.
  • moves follow the rules of tic tac toe.

Rust Solution

struct Solution;

impl Solution {
    fn tictactoe(moves: Vec<Vec<i32>>) -> String {
        let mut board = [[' '; 3]; 3];
        let mut player = 'X';
        let n = moves.len();
        for m in moves {
            let r = m[0] as usize;
            let c = m[1] as usize;
            board[r][c] = player;
            player = if player == 'X' { 'O' } else { 'X' };
        }
        let ss = [
            [(0, 0), (0, 1), (0, 2)],
            [(1, 0), (1, 1), (1, 2)],
            [(2, 0), (2, 1), (2, 2)],
            [(0, 0), (1, 0), (2, 0)],
            [(0, 1), (1, 1), (2, 1)],
            [(0, 2), (1, 2), (2, 2)],
            [(0, 0), (1, 1), (2, 2)],
            [(0, 2), (1, 1), (2, 0)],
        ];
        for s in &ss {
            let mut a = 0;
            let mut b = 0;
            for p in s {
                let i = p.0;
                let j = p.1;
                match board[i][j] {
                    'X' => a += 1,
                    'O' => b += 1,
                    _ => {}
                }
            }
            if a == 3 {
                return "A".to_string();
            }
            if b == 3 {
                return "B".to_string();
            }
        }
        if n == 9 {
            return "Draw".to_string();
        }
        "Pending".to_string()
    }
}

#[test]
fn test() {
    let moves = vec_vec_i32![[0, 0], [2, 0], [1, 1], [2, 1], [2, 2]];
    let res = "A".to_string();
    assert_eq!(Solution::tictactoe(moves), res);
    let moves = vec_vec_i32![[0, 0], [1, 1], [0, 1], [0, 2], [1, 0], [2, 0]];
    let res = "B".to_string();
    assert_eq!(Solution::tictactoe(moves), res);
    let moves = vec_vec_i32![
        [0, 0],
        [1, 1],
        [2, 0],
        [1, 0],
        [1, 2],
        [2, 1],
        [0, 1],
        [0, 2],
        [2, 2]
    ];
    let res = "Draw".to_string();
    assert_eq!(Solution::tictactoe(moves), res);
    let moves = vec_vec_i32![[0, 0], [1, 1]];
    let res = "Pending".to_string();
    assert_eq!(Solution::tictactoe(moves), res);
}

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