Code tidy-up (reduce unnecessary if statements in for loops)

[kleinebre]

In this file I noticed a for loop counting from 0..columns and subsequently doing nothing at index 0. In other words the loop spent doing a good number of unnecessary checks just because the starting point wasn't right.

I went over the rest of the file as well to further reduce unnecessary if statements inside loops which should enhance code efficiency, albeit sometimes at the cost of (partially) repeating code. I imagine speed may not be the top priority in this particular file, in which case no worries, but just pointing out that initial weirdness.

[liabru]

Thanks for the heads up but I feel your fix was a bit over-complicated for this, so I've done something simpler.