class Solution {public:    struct Loc    {        Loc(int rx, int ry)        {            x = rx; y = ry;        }        int x;        int y;    };    bool isOut(int x, int y, int width, int height)    {        if (x < 0 || x >= width) return true;        if (y < 0 || y >= height) return true;        return false;    }    void goSeed(vector<vector<char>> &board, int x, int y, int width, int height)    {        queue<Loc> q; q.push(Loc(x, y));        while (!q.empty())        {            int x0 = q.front().x;            int y0 = q.front().y;                        if (!isOut(x0 - 1, y0, width, height) && board[y0][x0 - 1] == ‘O‘)            {                q.push(Loc(x0 - 1, y0));                board[y0][x0 - 1] = ‘-‘;            }            if (!isOut(x0 + 1, y0, width, height) && board[y0][x0 + 1] == ‘O‘)            {                q.push(Loc(x0 + 1, y0));                board[y0][x0 + 1] = ‘-‘;            }            if (!isOut(x0, y0 - 1, width, height) && board[y0 - 1][x0] == ‘O‘)            {                q.push(Loc(x0, y0 - 1));                board[y0 - 1][x0] = ‘-‘;            }            if (!isOut(x0, y0 + 1, width, height) && board[y0 + 1][x0] == ‘O‘)            {                q.push(Loc(x0, y0 + 1));                board[y0 + 1][x0] = ‘-‘;            }            board[y0][x0] = ‘-‘;            q.pop();        }    }    void solve(vector<vector<char>> &board) {        if (board.empty()) return;        int height = board.size();        int width = board[0].size();                //    Check borders        for (int i = 0; i < width; i++)        {            if (board[0][i] == ‘O‘)    goSeed(board, i, 0, width, height);            if (board[height - 1][i] == ‘O‘)    goSeed(board, i, height - 1, width, height);        }        for (int i = 1; i < height - 1; i++)        {            if (board[i][0] == ‘O‘) goSeed(board, 0, i, width, height);            if (board[i][width - 1] == ‘O‘) goSeed(board, width - 1, i, width, height);        }        //            for (int i = 0; i < height; i++)        for (int j = 0; j < width; j++)        {            if (board[i][j] == ‘-‘) board[i][j] = ‘O‘;            else if (board[i][j] == ‘O‘) board[i][j] = ‘X‘;        }    }};