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+--- Thread: binary search string help (/thread-16647.html)
binary search string help - kietrichards - Mar-08-2019
Hi! I'm trying to look for a word in my list by way of binary search. But sth doesn;t work. Can sb have a look at it? ;) Thanks!
infile = open("clean.acc", "r")
firstlist = []
for line in infile:
firstlist.append(line)
first = 0
last = len(firstlist)-1
done = False
acc = input("Enter your acc nr")
while first<=last and not done:
mid = (first+last)//2
if firstlist[mid] == acc:
done = True
print(done)
else:
if firstlist[mid] > acc:
last = mid-1
else:
first = mid+1
infile.close()
RE: binary search string help - stullis - Mar-08-2019
Just a little refactoring and it works. I restructured the if statements into a single if...elif...else. The main problem was the mid assignment. Dividing by 2 generates a float and floats cannot be used in indexing; the interpreter would raise an error when trying firstlist[mid] because it's firstlist[4.5] (supposing a nine item list).
infile = open("clean.acc", "r")
firstlist = []
for line in infile:
firstlist.append(line)
first = 0
last = len(firstlist)-1
done = False
acc = input("Enter your acc nr")
while first<=last and not done:
mid = int((first+last)//2)
if acc < firstlist[mid]:
first = mid
elif acc == firstlist[mid]:
done = True
print(done)
else:
last = mid
infile.close()