Binary search recursive function not working if target is either the first, or last element in the a-CodePudding

I've been working on this recursive function in Ruby for quite some time now. There's one problem, which I can't seem to fix on my own.

def bsearch(array, target)
    pos = (array.length - 1) / 2
    return pos if array[pos] == target
    if array[pos] < target
        pos  = bsearch(array[pos..-1], target)
    else
        pos -= bsearch(array[0..pos], target)
    end
end

The code seems to work as long as the target isn't the first or last element in the array. I can't find the solution to this problem.

CodePudding user response：

The line

pos -= bsearch(array[0..pos], target)

should actually be

bsearch(array[0..pos], target)

If you think about it, if your array has length 200, and the item you are looking for is in position 5 of the first half of the array, it is also in position 5 of the wohle array.