binary search middle value calculation

Question

The following is the pseudocode I got from a TopCoder tutorial about binary search

binary_search(A, target):
   lo = 1, hi = size(A)
   while lo <= hi:
               


        

Answer 1

It is indeed possible for (hi+lo) to overflow integer. In the improved version, it may seem that subtracting lo from hi and then adding it again is pointless, but there is a reason: performing this operation will not overflow integer and it will result in a number with the same parity as hi+lo, so that the remainder of (hi+lo)/2 will be the same as (hi-lo)/2. lo can then be safely added after the division to reach the same result.