title: Divide and Conquer Matrix Multiplication
body: <p>I am having trouble getting divide and conquer matrix multiplication to work. From what I understand, you split the matrices of size nxn into quadrants (each quadrant is n/2) and then you do:   </p>
  
  <pre><code>C11 = A11⋅ B11 + A12 ⋅ B21   
  C12 = A11⋅ B12 + A12 ⋅ B22  
  C21 = A21 ⋅ B11 + A22 ⋅ B21  
  C22 = A21 ⋅ B12 + A22 ⋅ B22  
  </code></pre>
  
  <p>My output for divide and conquer is really large and I'm having trouble figuring out the problem as I am not very good with recursion.  </p>
  
  <p>example output:  </p>
  
  <p>Original Matrix A:  </p>
  
  <pre><code>4 0 4 3   
  5 4 0 4   
  4 0 4 0  
  4 1 1 1 
  </code></pre>
  
  <p>A x A  </p>
  
  <p>Classical:  </p>
  
  <pre><code>44 3 35 15  
  56 20 24 35  
  32 0 32 12  
  29 5 21 17  
  </code></pre>
  
  <p>Divide and Conquer:  </p>
  
  <pre><code>992 24 632 408  
  1600 272 720 1232   
  512 0 512 384  
  460 17 405 497  
  </code></pre>
  
  <p>Could someone tell me what I am doing wrong for divide and conquer? All my matrices are <code>int[][]</code> and classical method is the traditional 3 for loop matrix multiplication</p>