Problem 1698. Connect Four: find winning move

Created by Matthew Eicholtz

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Inspired by <a href = "http://www.mathworks.com/matlabcentral/cody/problems/90-connect-four-win-checker">this problem</a>...<a href = "http://en.wikipedia.org/wiki/Connect_Four">Connect Four</a> is a fun two-player game in which the goal is to be the first player to connect four pieces in a row - horizontally, vertically, or diagonally. Players take turns dropping one of their pieces into any of the available columns.Problem StatementGiven an array (size is arbitrary) in which<ul><li>0 : space is empty</li><li>1 : player 1 piece</li><li>2 : player 2 piece</li></ul>return the column that player 1 should play in to win the game. If there is more than one winning move, return a row vector of appropriate columns. If there are currently no winning moves, return [].Assumptions<ul><li>Pieces fall to the bottommost available row in each column, as in the real game</li><li>The input grid will always represent a valid game state</li></ul>ExampleIf<pre class="language-matlab">b = [0 0 0 0 0 0 0;
 0 0 0 0 0 0 0;
 0 0 0 2 0 0 0;
 0 0 0 1 0 0 0;
 0 0 0 2 2 0 0;
 0 0 2 1 1 1 0];
</pre>then<pre class="language-matlab">y = 7
</pre>

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101 Solutions
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Last Solution submitted on Mar 19, 2021

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Solution 276412

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Richard Zapor on 14 Jul 2013

Very creative usage of blkdiag in collaboration with conv2. I prefer nnz over "any" for speed and compactness.

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