<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:

    void oMarker(int r,int c,vector<vector<char>>& board,vector<vector<bool>>& vis) {
        int n=board.size(),m=board[0].size();
        queue<pair<int,int>> q;
        q.push({r,c});
        vis[r][c]=true;

        while(!q.empty()) {
            vector<int> I={1,0,-1,0},J={0,1,0,-1};
            int r=q.front().first,c=q.front().second;
            q.pop();

            for(int i=0;i<4;i++) {
                int nr=r+I[i],nc=c+J[i];
                if(nr<0 || nc<0 || nr>=n || nc>=m) continue;
                if(board[nr][nc]=='O' && !vis[nr][nc]) {
                    q.push({nr,nc});
                    vis[nr][nc]=true;
                }
            }
        }
    }

    void solve(vector<vector<char>>& board) {
        int n=board.size(),m=board[0].size();
        vector<vector<bool>> vis(n,vector<bool>(m,false));
        for(int i=0;i<n;i++) {
            if(board[i][0]=='O') oMarker(i,0,board,vis);
            if(board[i][m-1]=='O') oMarker(i,m-1,board,vis);
        }
        for(int i=0;i<m;i++) {
            if(board[0][i]=='O') oMarker(0,i,board,vis);
            if(board[n-1][i]=='O') oMarker(n-1,i,board,vis);
        }
        for(int i=1;i<n-1;i++) {
            for(int j=1;j<m-1;j++) {
                if(board[i][j]=='O' && !vis[i][j]) board[i][j]='X';
                cout<<vis[i][j]<<" ";
            }
            cout<<endl;
        }
    }
};
16763