<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 rows;
    int cols;
    void solve(vector<vector<char>>& board) {
        // get rows & cols size
        rows = board[0].size();
        cols = board.size();
        // have another function which is dfs, this will change the border(play with limits) connected O to I
        for(int i=0;i<cols;i++){
            changeBorderConnected(board,i,0);
            changeBorderConnected(board,i,rows-1);
        }
        for(int i=0;i<rows;i++){
            changeBorderConnected(board,0,i);
            changeBorderConnected(board,cols-1,i);
        }
        for(int i=1;i<cols-1;i++){
            for(int j=1;j<rows-1;j++)
                destory(board,i,j);
        }
        for(int i=0;i<cols;i++){
            changeBackBorderConnected(board,i,0);
            changeBackBorderConnected(board,i,rows-1);
        }
        for(int i=0;i<rows;i++){
            changeBackBorderConnected(board,0,i);
            changeBackBorderConnected(board,cols-1,i);
        }
        // call the same on horizontolly right & left: vertically top & down
        // have another dfs this will change O to X limit is expect the border
        // now change back to original for border connected

    }

    void changeBorderConnected(vector<vector<char>>& board, int i, int j){
        if(i<0||j<0||i>=cols||j>=rows || board[i][j]=='X'||board[i][j]=='I')
            return;
        board[i][j]='I';
        changeBorderConnected(board,i+1,j);
        changeBorderConnected(board,i-1,j);
        changeBorderConnected(board,i,j+1);
        changeBorderConnected(board,i,j-1);
    }

    void destory(vector<vector<char>>& board, int i, int j){
        if(i<0||j<0||i>=cols||j>=rows || board[i][j]=='X'||board[i][j]=='I')
            return;
        board[i][j]='X';
        destory(board,i+1,j);
        destory(board,i-1,j);
        destory(board,i,j+1);
        destory(board,i,j-1);
    }

    void changeBackBorderConnected(vector<vector<char>>& board, int i, int j){
        if(i<0||j<0||i>=cols||j>=rows || board[i][j]=='X'|| board[i][j]=='O')
            return;
        
        board[i][j]='O';
        changeBackBorderConnected(board,i+1,j);
        changeBackBorderConnected(board,i-1,j);
        changeBackBorderConnected(board,i,j+1);
        changeBackBorderConnected(board,i,j-1);
    }
};
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