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new node’s next, as shown in Figure 18.9b. The size is now increased by
1 (line 133).
head
current
temp
tail
e 0
next
…
e i
next
A new node
to be inserted
here
e i+1
…
next
None
e
(a) Before a n ew node is inserted.
None
e k
head
current
temp
tail
e 0
next
…
e i
next
e i+1
next
…
e k
None
A new node
is inserted in
the list
e
None
(b) After a new node is inserted.
Figure 18.9
A new element is inserted in the middle of the list.
18.2.2.4 Implementing removeFirst()
The removeFirst() method is to remove the first element from the list.
It can be implemented as follows:
1 def removeFirst(self):
2 if self.__size == 0:
3 return None # Nothing to delete
4 else:
5 temp = self.__head # Keep the first node temporarily
6 self.__head = self.__head.next # Move head to point the next
7 self.__size -= 1 # Reduce size by 1
8 if self.__head == None:
9 self.__tail = None # List becomes empty
10 return temp.element # Return the deleted element
Consider two cases:
(1) If the list is empty, there is nothing to delete, so return None
(line 3);
12
© Copyright 2012 by Pearson Education, Inc. All Rights Reserved.