Singly Linked List
A singly linked list is a linear collection of data elements that can only be traversed in one direction. Each node has a ‘value’ field and a ‘next’ field. The value field stores any type of value, and the next field points to the next node. The linked list will return ‘None’ after the last node.
Python Code
Create Singly Linked List
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
def __repr__(self):
return self.val
class LinkedList:
def __init__(self, nodes=None):
self.val = None
if nodes is not None:
node = ListNode(val=nodes.pop(0))
self.val = node
for elem in nodes:
node.next = ListNode(val=elem)
node = node.next
def __repr__(self):
node = self.val
nodes = []
while node is not None:
nodes.append(node.val)
node = node.next
nodes.append("None")
return " -> ".join(nodes)
def __iter__(self):
node = self.val
while node is not None:
yield node
node = node.next
# build a single linked list
list = LinkedList(["12", "99", "37"])
list
# output
# 12 -> 99 -> 37 -> None
# loop to extract elements in list
for node in list:
print(node)
# output
# 12
# 99
# 37
# current node and move to next node
node = list.val
print(node)
node = node.next
print(node)
# output
# 12
# 99
# return after the last node
node = list.val.next.next.next
print(node)
# output
# None
