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Wrote this code in comp sci class and I cant get it to work. Its supposed to be a recursive binary search method... Any idea why I can't get it to work?

 arr = [1,10,12,15,16,122,132,143,155]

def binarysearch(arr,num):
    arr2 = []
    for i in range (len(arr)/2):
        arr2.append(0)
    if (arr[len(arr)/2]>num):
        for x in range (len(arr)/2,len(arr)):
            arr2[x-(len(arr)/2)]=arr[x]
        binarysearch(arr2,num)
    if(arr[len(arr)/2]<num):
        for x in range(0, len(arr) / 2 ):
            arr2[x] = arr[x]
        binarysearch(arr2, num)
    if(len(arr)==1):
        if(arr[0]==num):
            return 1
        else:
            return 0


num = raw_input("put number to check here please: ")
if(binarysearch(arr,num)==1):
    print "true"
else:
    print "false"
Improve this question
4
  • At a glance, your first two if blocks look suspicious to me. When you recursively call a function, if you want both calls to terminate when the inner call returns, then you need a return statement: return binarysearch(arr2,num) Commented Mar 8, 2018 at 14:31
  • Related reading: Why does my function return None? Commented Mar 8, 2018 at 14:33
  • You should probably clarify what you mean by "it doesn't work". Commented Mar 8, 2018 at 14:34
  • I'm not sure why you are creating a new array and appending to that for a binary search. Here's a neat solution - stackoverflow.com/a/46080558/6089653 Commented Mar 8, 2018 at 15:08
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