title: Matrix spiral traversal subset sum
body: <p>Given a matrix find the subset sum while traversing matrix in spiral form.</p>
  
  <p>Was asked this question in an interview. Figured this is a combination of traversing in spiral form in O(n) and find subset sum (exponential or DP solution). But unable to think how can i combine both solution. Any pointers are appreciated.</p>
  
  <p>EDIT: No extra space allowed.</p>