<p>You are given an <code>m x n</code> matrix <code>board</code> containing <strong>letters</strong> <code>&#39;X&#39;</code> and <code>&#39;O&#39;</code>, <strong>capture regions</strong> that are <strong>surrounded</strong>:</p>

<ul>
	<li><strong>Connect</strong>: A cell is connected to adjacent cells horizontally or vertically.</li>
	<li><strong>Region</strong>: To form a region <strong>connect every</strong> <code>&#39;O&#39;</code> cell.</li>
	<li><strong>Surround</strong>: The region is surrounded with <code>&#39;X&#39;</code> cells if you can <strong>connect the region </strong>with <code>&#39;X&#39;</code> cells and none of the region cells are on the edge of the <code>board</code>.</li>
</ul>

<p>A <strong>surrounded region is captured</strong> by replacing all <code>&#39;O&#39;</code>s with <code>&#39;X&#39;</code>s in the input matrix <code>board</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">board = [[&quot;X&quot;,&quot;X&quot;,&quot;X&quot;,&quot;X&quot;],[&quot;X&quot;,&quot;O&quot;,&quot;O&quot;,&quot;X&quot;],[&quot;X&quot;,&quot;X&quot;,&quot;O&quot;,&quot;X&quot;],[&quot;X&quot;,&quot;O&quot;,&quot;X&quot;,&quot;X&quot;]]</span></p>

<p><strong>Output:</strong> <span class="example-io">[[&quot;X&quot;,&quot;X&quot;,&quot;X&quot;,&quot;X&quot;],[&quot;X&quot;,&quot;X&quot;,&quot;X&quot;,&quot;X&quot;],[&quot;X&quot;,&quot;X&quot;,&quot;X&quot;,&quot;X&quot;],[&quot;X&quot;,&quot;O&quot;,&quot;X&quot;,&quot;X&quot;]]</span></p>

<p><strong>Explanation:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/xogrid.jpg" style="width: 367px; height: 158px;" />
<p>In the above diagram, the bottom region is not captured because it is on the edge of the board and cannot be surrounded.</p>
</div>

<p><strong class="example">Example 2:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">board = [[&quot;X&quot;]]</span></p>

<p><strong>Output:</strong> <span class="example-io">[[&quot;X&quot;]]</span></p>
</div>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == board.length</code></li>
	<li><code>n == board[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 200</code></li>
	<li><code>board[i][j]</code> is <code>&#39;X&#39;</code> or <code>&#39;O&#39;</code>.</li>
</ul>

class Solution {
public:
    int edgectrl(vector<vector<char>>&board,int row,int col){
        if (row==0||col==0||row==board.size()-1||col==board[0].size()-1){
            return 0;
        }    
        return 1;
    
    }
    void marker(vector<vector<char>>&board,int row,int col,int &mark){
        mark*=edgectrl(board,row,col);
        board[row][col]='Y';
        if(row>0&&board[row-1][col]=='O')marker(board,row-1,col,mark);
        if(row<board.size()-1&&board[row+1][col]=='O')marker(board,row+1,col,mark);
        if(col>0&&board[row][col-1]=='O')marker(board,row,col-1,mark);
        if(col<board[0].size()-1&&board[row][col+1]=='O')marker(board,row,col+1,mark);
        
    }
    void alter_board(vector<vector<char>>& board,int row,int col){
        board[row][col]='X';
        if(row>0&&board[row-1][col]=='Y')alter_board(board,row-1,col);
        if(row<board.size()-1&&board[row+1][col]=='Y')alter_board(board,row+1,col);
        if(col>0&&board[row][col-1]=='Y')alter_board(board,row,col-1);
        if(col<board[0].size()-1&&board[row][col+1]=='Y')alter_board(board,row,col+1);
    }
    void solve(vector<vector<char>>& board) {
        int mark =0;
        for(int i=0;i<board.size();i++){
            for(int j=0;j<board[0].size();j++){
                if (board[i][j]=='O'){
                    mark=1;
                    marker(board,i,j,mark);
                    if (mark)
                    alter_board(board,i,j);
                }
            }
        }
        for(int i=0;i<board.size();i++){
            for(int j=0;j<board[0].size();j++){
                if (board[i][j]=='Y'){
                    board[i][j]='O';    
                }
            }
        }
    }
};
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