Fixed algo3--should get correct outputs now

The main change I made was to reorder algo 3. For the left/right calculations, I made them start at the midpoint and go down/up. 

I also changed the initial value for the sums since if it starts out negative I think 0 could throw it off. Not sure how much that affects the final solution though.

There's still a small bug where algo1 has a different value. Other than that I think they show the same results.