Sparse Matrix Multiplication

Given two sparse matrices A and B, return the result of AB.

You may assume that A‘s column number is equal to B‘s row number.

Example:

  1. A = [
  2.   [ 1, 0, 0],
  3.   [-1, 0, 3]
  4. ]
  6. B = [
  7.   [ 7, 0, 0 ],
  8.   [ 0, 0, 0 ],
  9.   [ 0, 0, 1 ]
  10. ]
  13.      |  1 0 0 |   | 7 0 0 |   |  7 0 0 |
  14. AB = | -1 0 3 | x | 0 0 0 | = | -7 0 3 |
  15.                   | 0 0 1 |