def __getitem__(self: 'LinkedList', ind: int) -> object:
"""Return the item at position ind.
Raise exception if ind is out-of-range
>>> lnk = LinkedList(5, LinkedList(7, LinkedList(11, LinkedList())))
>>> lnk[1]
7
"""
if self.empty or ind < 0:
raise IndexError
elif ind > 0:
return self.rest.__getitem__(ind - 1)
else:
return self.item
Friday, 7 March 2014
Week 8
This week in CSC148, we focused mainly on linked structures. In the lab, we had to make methods for a LinkedList class including __len__, __setitem__, __delitem__, and insert. The trouble was that the only two helpful methods already built were prepend and decapitate, so we were required to use recursion. This was a bit different than the recursion I have been exposed to so far. We had to kind of count down through the indices i of the LinkedList until 0 was reached, calling the function on i - 1 each time, in order to reach the recursion depth that we wanted to insert at, or set, or delete. Here is the method __getitem__, which demonstrates what I'm trying to say:
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Simple and elegant. Nice work.
ReplyDeleteWere you precluded from using iteration? The example above could also have been written iteratively - no? The core logic would have been something like (not carefully checked, and sorry for the syntax, don't know python):
while(!self.empty && ind > 0)
{
self=self.rest;
ind = ind-1;
}
if self.empty raise IndexError
else return self.item