Here is the problem: What is returned by newSnake are two
positions (x, k+x). These two positions are 'folded' here into one int. snake2x() and snake2y() are used to 'unfold'. Stress test of the diff algorithm have shown that we reach the limits of int quite soon (when diffing strings of 100k size). Snakes should become pairs of ints. I'll post a fix for this