leetcode - surrounding regions

surroundedregions.java

public class Solution {
    private static int M;
    private static int N;
    
    public void solve(char[][] board) {
        M = board.length;
            N = board[0].length;
            //graph = new Node[M, N];
            for (int i = 0; i < M; i++)
                for (int j = 0; j < N; j++)
                    if (board[i][j] == 'O')
                        MarkRegions(board, i, j);
        
    }
    
        static boolean CheckTop(char[][] board, int m, int n)
        {
            boolean isBounded = false;
            //scan top
            if (m - 1 >= 0)
            {
                if (board[m - 1][n] == 'O')
                    isBounded = CheckTop(board, m - 1, n);
                else
                    isBounded = true;
            }
            return isBounded;
        }

        static boolean CheckBottom(char[][] board, int m, int n)
        {
            boolean isBounded = false;
            if (m + 1 < M)
            {
                if (board[m + 1][n] == 'O')
                    isBounded = CheckBottom(board, m + 1, n);
                else
                    isBounded = true;
            }
            return isBounded;
        }

        static boolean CheckLeft(char[][] board, int m, int n)
        {
            boolean isBounded = false;
            if (n - 1 >= 0)
            {
                if (board[m][n - 1] == 'O')
                    isBounded = CheckLeft(board, m, n - 1);
                else
                    isBounded = true;
            }
            return isBounded;
        }

        static boolean CheckRight(char[][] board, int m, int n)
        {
            boolean isBounded = false;
            if (n + 1 < N)
            {
                if (board[m][n + 1] == 'O')
                    isBounded = CheckRight(board, m, n + 1);
                else
                    isBounded = true;
            }
            return isBounded;
        }

        static void MarkRegions(char[][] board, int m, int n)
        {
            boolean result = CheckTop(board,m,n) && CheckBottom(board,m,n) && CheckLeft(board,m,n) && CheckRight(board,m,n);
            if (result)
                board[m][n] = 'X';
        }
}