<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:

    def __init__(self):
        self.not_region = set()

    def solve(self, grid: List[List[str]]) -> None:
        """
        Do not return anything, modify board in-place instead.
        """
        for i in range(1, len(grid) - 1):
            for j in range(1, len(grid[0]) - 1):
                if grid[i][j] == 'O':
                    temp = set()
                    found = self.find(grid, i , j, temp)
                    if len(temp)>0 and not found:
                        for ele in temp:
                            split = ele.split()
                            row = int(split[0])
                            col = int(split[1])
                            grid[row][col] = 'O'
    
    def find(self, grid, i, j, temp):
        if f'{str(i)} {str(j)}' in self.not_region:
            print(True)
            return
        if i == len(grid)  or j == len(grid[0]) or i == -1 or j == -1:
            return False
        if grid[i][j] == 'X':
            return True

        grid[i][j] = 'X'   
        temp.add(f'{str(i)} {str(j)}')
        r = self.find(grid, i, j+1, temp)
        d = self.find(grid, i+1, j, temp)
        l = self.find(grid, i, j-1, temp)
        u = self.find(grid, i-1, j, temp)
        
        if r and d and u and l:
            return True
        else: 
            grid[i][j] = 'O'
            self.not_region.add(f'{str(i)} {str(j)}')
            temp.remove(f'{str(i)} {str(j)}')
            return False
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