Zig-zag matrix
A 'zig-zag' array is a square arrangement of the first $N^2$ integers, where the numbers increase sequentially as you zig-zag along the array's anti-diagonals.
For example, for the input 5, the following result should be produced:
0 1 5 6 14 2 4 7 13 15 3 8 12 16 21 9 11 17 20 22 10 18 19 23 24
Test
{{test}}Console output