Just use secondary diagonals of (1,1), (2,2),...,(n,n) matrixs (this wasn't regular plural of noun matrix , excuse me for my grammar).

p.s that was my way, maybe there is another

Edited by author 05.05.2005 07:06

More Hint: Maybe you can use BFS. Enqueue position adjacent to itself.

But think of which one could be enqueued first.

i agree, and then recursively call print function to walk through every pixel.. very easy problem,, got AC