1. An “abstract” view of the stack:
Using an array implementation would look something like:
items: a b c
0 1 2 3 (max-1)
top: max:
2100
Complete the big-oh notation for the following stack methods assuming an array implementation: ("n" is the # items)
Big-oh
ConstructorisFull( )isEmpty( ) size( )peek( )pop( )push(item)
2. Since Python does not have a (directly accessable) built-in array, we can use a list.
class Stack:
def __init__(self):
self.items = []
def isEmpty(self):
return self.items == []
def push(self, item):
self.items.append(item)
def pop(self):
return self.items.pop()
def peek(self):
return self.items[len(self.items)-1]
def size(self):
return len(self.items)
Since Python uses an array of references (pointers) to list items in their implementation of a list.
a
b
c top
bottom
Stack
"Abstract"
items:
Stack Object
list Object
a b c
0 1 2 3
a) Complete the big-oh notation for the stack methods assuming this Python list implementation: ("n" is the # items)
Big-oh
__init__isEmpty( ) size( )peek( )pop( )push(item)
b) Which operations should have what preconditions?
Data Structures (CS 1520) Lecture 4 Name:_________________
Lecture 4 - Page 1
a
b
c top
bottom
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