<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 solve(vector<vector<char>>& board) {
        if(board.empty() || board[0].empty())
        {
            return;
        }

        for(int i = 0; i < board.size(); i++)
        {
            for(int j = 0; j < board[0].size(); j++)
            {
                if(board[i][j] == 'O')
                {
                    bool check = false;
                    vector<pair<int,int>> toRun;

                    queue<pair<int,int>> traverse;

                    traverse.emplace(i,j);

                    while(!traverse.empty())
                    {
                        int x = traverse.front().first;
                        int y = traverse.front().second;
                        traverse.pop();

                        if(x < 0 || x >= board.size() || y < 0 || y >= board[0].size())
                        {
                            check = true;
                            continue;
                        }

                        if(board[x][y] != 'O')
                        {
                            continue;
                        }
                        board[x][y] = 'S';

                        toRun.push_back({x,y});

                        traverse.emplace(x-1,y);
                        traverse.emplace(x+1,y);
                        traverse.emplace(x,y - 1);
                        traverse.emplace(x,y + 1);
                    }

                    if(!check)
                    {
                        for(auto &i: toRun)
                        {
                            board[i.first][i.second] = 'X';
                        }
                    }
                }
            }
        }
        for(int i = 0; i < board.size(); i++)
        {
            for(int j = 0; j < board[0].size(); j++)
            {
                if(board[i][j] == 'S')
                {
                   board[i][j] = 'O';
                }
            }
        }
    }
};
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