LeetCode //C - 1275. Find Winner on a Tic Tac Toe Game

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. The rules of Tic-Tac-Toe are:

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 three 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 a 2D integer array moves where m o v e s $i$ = $r o w i , c o l i$ moves $i$ = $row_i, col_i$ moves $i$ = $rowi,coli$ indicates that the i t h i^{th} ith move will be played on g r i d $r o w i$ $c o l i$ grid $row_i$ $col_i$ grid $rowi$ $coli$ . 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 (i.e., 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, they always play first.

Example 2:

Input: moves = $\[0,0$ , $1,1$ , $0,1$ , $0,2$ , $1,0$ , $2,0$ ]

Output: "B"

Explanation: TB wins.

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.

Constraints:

1 <= moves.length <= 9
moves $i$ .length == 2
0 < = r o w i , c o l i < = 2 0 <= row_i, col_i <= 2 0<=rowi,coli<=2
There are no repeated elements on moves.
moves follow the rules of tic tac toe.

From: LeetCode

Link: 1275. Find Winner on a Tic Tac Toe Game

Solution:

Ideas:

put A as 1, B as -1.

If any row, column, or diagonal sums to 3, A wins.

If it sums to -3, B wins.

Code:

c 复制代码

char* tictactoe(int** moves, int movesSize, int* movesColSize) {
    int board[3][3] = {0}; // A = 1, B = -1

    for (int i = 0; i < movesSize; i++) {
        int r = moves[i][0];
        int c = moves[i][1];

        board[r][c] = (i % 2 == 0) ? 1 : -1;
    }

    for (int i = 0; i < 3; i++) {
        int row = board[i][0] + board[i][1] + board[i][2];
        int col = board[0][i] + board[1][i] + board[2][i];

        if (row == 3 || col == 3) return "A";
        if (row == -3 || col == -3) return "B";
    }

    int diag1 = board[0][0] + board[1][1] + board[2][2];
    int diag2 = board[0][2] + board[1][1] + board[2][0];

    if (diag1 == 3 || diag2 == 3) return "A";
    if (diag1 == -3 || diag2 == -3) return "B";

    if (movesSize == 9) return "Draw";
    return "Pending";
}