Bifalgorithm post

15 numbers, sorted. Find 29, fast. Check them one by one. 15 checks. Watch this instead. Two flags mark where the answer can live. Check the middle. 23. 23 is under 29. So everything on the left is out. Eight cells, gone. One comparison, cut the world in half. Middle of what's left, 35. Over 29, so the right side goes. Opposite direction, same trick. Three cells remain. Middle, 29. Found. Three checks, That's the whole search. 15 checks or three. Oh of N or O of log N. Cut the problem in half every time.

15 numbers, sorted. Find 29, fast. Check them one by one. 15 checks. Watch this instead. Two flags mark where the answer can live. Check the middle. 23. 23 is…