Hi, here's your problem today. This problem was recently asked by Amazon:

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You are given a 2D array of integers. Print out the clockwise spiral traversal of the matrix.

Example:

<pre lang=py>
grid = [[1,  2,  3,  4,  5],
        [6,  7,  8,  9,  10],
        [11, 12, 13, 14, 15],
        [16, 17, 18, 19, 20]]
</pre>

The clockwise spiral traversal of this array is:

<pre lang=py>
1, 2, 3, 4, 5, 10, 15, 20, 19, 18, 17, 16, 11, 6, 7, 8, 9, 14, 13, 12
</pre>

Here is a starting point:

<pre lang=py>
def matrix_spiral_print(M):
  # Fill this in.

grid = [[1,  2,  3,  4,  5],
        [6,  7,  8,  9,  10],
        [11, 12, 13, 14, 15],
        [16, 17, 18, 19, 20]]

matrix_spiral_print(grid)
# 1 2 3 4 5 10 15 20 19 18 17 16 11 6 7 8 9 14 13 12
</pre>