Print spiral on matrix
Given a square matrix, print out the contents in clockwise order. For example:
1
1
+++
1 2
3 4
1 2 4 3
+++
1 2 3
4 5 6
7 8 9
1 2 3 6 9 8 7 4 5
+++
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
1 2 3 4 8 12 16 15 14 13 9 5 6 7 11 10
+++
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
21 22 23 24 25
1 2 3 4 5 10 15 20 25 24 23 22 21 16 11 6 7 8 9 14 19 18 17 12 13
+++