1var solve = function(board) {
2    function dfs(row, col) {
3        if (row < 0 || col < 0 || row >= m || col >= n || board[row][col] !== 'O') return;
4        board[row][col] = 'A';
5        dfs(row - 1, col);
6        dfs(row + 1, col);
7        dfs(row, col - 1);
8        dfs(row, col + 1);
9    }
10
11    let m = board.length;
12    if (m === 0) return;
13    let n = board[0].length;
14
15    for (let i = 0; i < m; i++) {
16        if (board[i][0] === 'O') dfs(i, 0);
17        if (board[i][n - 1] === 'O') dfs(i, n - 1);
18    }
19
20    for (let j = 0; j < n; j++) {
21        if (board[0][j] === 'O') dfs(0, j);
22        if (board[m - 1][j] === 'O') dfs(m - 1, j);
23    }
24
25    for (let i = 0; i < m; i++) {
26        for (let j = 0; j < n; j++) {
27            if (board[i][j] === 'O') board[i][j] = 'X';
28            if (board[i][j] === 'A') board[i][j] = 'O';
29        }
30    }
31};

1using System;
2using System.Collections.Generic;

public class Solution {
    private void Bfs(char[][] board, int row, int col, int m, int n) {
        Queue<(int, int)> q = new Queue<(int, int)>();
        q.Enqueue((row, col));
        board[row][col] = 'A';

        while (q.Count > 0) {
            var (curRow, curCol) = q.Dequeue();

            int[][] directions = new int[][] {
                new int[] {1, 0},
                new int[] {-1, 0},
                new int[] {0, 1},
                new int[] {0, -1}
            };

            foreach (var dir in directions) {
                int newRow = curRow + dir[0];
                int newCol = curCol + dir[1];
                if (newRow >= 0 && newRow < m && newCol >= 0 && newCol < n && board[newRow][newCol] == 'O') {
                    board[newRow][newCol] = 'A';
                    q.Enqueue((newRow, newCol));
                }
            }
        }
    }

    public void Solve(char[][] board) {
        int m = board.Length;
        if (m == 0) return;
        int n = board[0].Length;

        for (int i = 0; i < m; i++) {
            if (board[i][0] == 'O') Bfs(board, i, 0, m, n);
            if (board[i][n - 1] == 'O') Bfs(board, i, n - 1, m, n);
        }

        for (int j = 0; j < n; j++) {
            if (board[0][j] == 'O') Bfs(board, 0, j, m, n);
            if (board[m - 1][j] == 'O') Bfs(board, m - 1, j, m, n);
        }

        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (board[i][j] == 'O') board[i][j] = 'X';
                if (board[i][j] == 'A') board[i][j] = 'O';
            }
        }
    }
}