Kata

In this kata, you'll have to write a function multiply(int[][], int[][]) -> int[][] that multiplies two matrices. The matrices are represented by arrays of rows, where each row is an int[]. For example, the 3x3 identity represented this way would be:

int[][] ident = new int[][] {
  new int[] {1, 0, 0},
  new int[] {0, 1, 0},
  new int[] {0, 0, 1}
};

Of course, there's a catch: you only get one semicolon!

All the matrices you receive are guaranteed to be valid matrices (i.e. you won't get rows of varying sizes in the same matrix). If a particular multiplication is impossible, your function should return null. The input arrays will not be empty.

For your convenience, a utility function Utils.print(int[][]) -> void has been provided. If you pass it a matrix, it'll print it to the console in a somewhat readable fashion. Remember to remove any debug code in your final answer, though -- can't have any stray semicolons!

Good luck!