Given a matrix where row i corresponds to person i, and column j corresponds to task j and cell (i,j) corresponds to the time taken for person i to complete task j. Output an assignment array for the minimal time taken for all tasks.

For example, if presented with the following matrix:

 x = [1,3,4,7;  
      2,3,1,3;
      4,2,3,7;
      6,4,2,2;]

Your output array would be:

 a = [1,3,2,4].

Where person one is assigned to task one, person three is assigned to task two , person two is assigned to task three and person four is assigned to task four.

This gives us a total time of 1+1+2+2=6 which is minimal.