<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 bfs1(int i, int j, vector<vector<char>>& landscape,
              map<vector<int>, int>& visited) {
        if (j + 1 <= landscape[i].size() - 1 && landscape[i][j + 1] == 'O' &&
            visited.count({i, j + 1}) == 0) {
            visited[{i, j + 1}] = 1;
            bfs1(i, j + 1, landscape, visited);
        }
        if (i + 1 <= landscape.size() - 1 && landscape[i + 1][j] == 'O' &&
            visited.count({i + 1, j}) == 0) {
            visited[{i + 1, j}] = 1;
            bfs1(i + 1, j, landscape, visited);
        }
        if (i - 1 >= 0 && landscape[i - 1][j] == 'O' &&
            visited.count({i - 1, j}) == 0) {
            visited[{i - 1, j}] = 1;
            bfs1(i - 1, j, landscape, visited);
        }
        if (j - 1 >= 0 && landscape[i][j - 1] == 'O' &&
            visited.count({i, j - 1}) == 0) {
            visited[{i, j - 1}] = 1;
            bfs1(i, j - 1, landscape, visited);
        }
    }
    void solve(vector<vector<char>>& board) {
        int i = 0;
        int j = 0;
        map<vector<int>, int> visited;
        if (i == 0 && j == 0) {
            for (; j < board[0].size(); j++) {
                if (board[i][j] == 'O' && visited.count({i, j}) == 0) {
                    visited[{i, j}] = 1;
                    bfs1(i, j, board, visited);
                }
            }
            j--;
            i++;
        }
        if (i == 1 && j == board[0].size() - 1) {
            for (; i < board.size(); i++) {
                if (board[i][j] == 'O' && visited.count({i, j}) == 0) {
                    visited[{i, j}] = 1;
                    bfs1(i, j, board, visited);
                }
            }
            i--;
            j--;
        }
        if (i == board.size() - 1 && j == board[0].size() - 2) {
            for (; j >= 0; j--) {
                if (board[i][j] == 'O' && visited.count({i, j}) == 0) {
                    visited[{i, j}] = 1;
                    bfs1(i, j, board, visited);
                }
            }
            j++;
            i--;
        }
        if (i == board.size() - 2 && j == 0) {
            for (; i > 0; i--) {
                if (board[i][j] == 'O' && visited.count({i, j}) == 0) {
                    visited[{i, j}] = 1;
                    bfs1(i, j, board, visited);
                }
            }
        }
        for (int r = 0; r < board.size(); r++) {
            for (int c = 0; c < board[0].size(); c++) {
                if (board[r][c] == 'O' && visited.count({r, c}) == 0) {
                    board[r][c] = 'X';
                }
            }
        }
    }
};
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