<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 solve(self, board: List[List[str]]) -> None:
        """
        Do not return anything, modify board in-place instead.
        """
        b=board
        w=len(b)
        l=len(b[0])
        DD={(i,j):0 for i in range(w) for j in range(l)}
        D1={(i,j):"NE" for i in range(w) for j in range(l)}
        def adj(i,j):
            la=[]
            ll=[(i+1,j),(i,j+1),(i-1,j),(i,j-1)]
            for s in ll:
                if s[0]>=0 and s[0]<=w-1 and s[1]>=0 and s[1]<=l-1:
                    if b[s[0]][s[1]]=="O":
                        la.append(s)
            return la
        
        def DFStill(i,j):
            pc.add((i,j))
            DD[(i,j)]=1
            D1[(i,j)]="E"
            for s in adj(i,j):
                a,b=s
                if DD[(a,b)]==0:
                    DFStill(a,b)

        pc=set()
        l1=[(0,j) for j in range(l)]
        l2=[(w-1,j) for j in range(l)]
        l3=[(i,0) for i in range(w)]
        l4=[(i,l-1) for i in range(w)]
        ll=l1+l2+l3+l4
        for s in ll:
            i,j=s
            if b[i][j]=="O" and DD[(i,j)]==0:
                #print("got here, (i,j) is", (i,j))
                DFStill(i,j)
                #print("now,(i,j) is",(i,j), "issurrounded is", issurrounded, "potentialcapture is", potentialcapture)
        for i in range(w):
            for j in range(l):
                if b[i][j]=="O":
                    if D1[(i,j)]=="NE":
                        b[i][j]="X"

        
        
26390