<p>Let's play the minesweeper game (<ahref="https://en.wikipedia.org/wiki/Minesweeper_(video_game)"target="_blank">Wikipedia</a>, <ahref="http://minesweeperonline.com"target="_blank">online game</a>)!</p>
<p>You are given an <code>m x n</code> char matrix <code>board</code> representing the game board where:</p>
<ul>
<li><code>'M'</code> represents an unrevealed mine,</li>
<li><code>'E'</code> represents an unrevealed empty square,</li>
<li><code>'B'</code> represents a revealed blank square that has no adjacent mines (i.e., above, below, left, right, and all 4 diagonals),</li>
<li>digit (<code>'1'</code> to <code>'8'</code>) represents how many mines are adjacent to this revealed square, and</li>
<li><code>'X'</code> represents a revealed mine.</li>
</ul>
<p>You are also given an integer array <code>click</code> where <code>click = [click<sub>r</sub>, click<sub>c</sub>]</code> represents the next click position among all the unrevealed squares (<code>'M'</code> or <code>'E'</code>).</p>
<p>Return <em>the board after revealing this position according to the following rules</em>:</p>
<ol>
<li>If a mine <code>'M'</code> is revealed, then the game is over. You should change it to <code>'X'</code>.</li>
<li>If an empty square <code>'E'</code> with no adjacent mines is revealed, then change it to a revealed blank <code>'B'</code> and all of its adjacent unrevealed squares should be revealed recursively.</li>
<li>If an empty square <code>'E'</code> with at least one adjacent mine is revealed, then change it to a digit (<code>'1'</code> to <code>'8'</code>) representing the number of adjacent mines.</li>
<li>Return the board when no more squares will be revealed.</li>
<li><code>board[i][j]</code> is either <code>'M'</code>, <code>'E'</code>, <code>'B'</code>, or a digit from <code>'1'</code> to <code>'8'</code>.</li>
