LinkedList.py

# In Python we deal with data structures like lists,
# but we don't talk much about how lists are implemented
# by Python itself.
#
# One way in which lists can be implemented is with what
# is called a Linked List. In a Linked List, a list is
# made of a series of items. Each item contains two
# elements: its own value (node.value), and a pointer to
# where to find the next element in the list
# (node.next_node). So, you can't jump right in to
# "item 7"; you instead have to start with the first
# item and keep getting the next item until you reach the
# seventh item.
#
# Below is some code we've written to implement a
# Linked List. Specifically, this code represents a
# single node in a linked list: a full list is created
# just by chaining nodes like these together. The last
# node in the linked list will point to None as the
# next item; that indicates you've reached the end of
# the linked list.
#
# Write a function called linked_list_search. Your
# linked_list_search function should take two parameters:
# a single linked list node, and a search term. Your
# function should return True if the search term is the
# value of the linked list node or any node after it.
# It should return False if the value is not found in
# the linked list.

class LinkedListNode:
    def __init__(self, value, next_node=None):
        self.value = value
        self.next_node = next_node


def linked_list_search(root_node, value: int) -> bool:
    """Returns True if value in linked list, otherwise False."""

    current_node = root_node
    while current_node is not None:
        if current_node.value == value:
            return True

        current_node = current_node.next_node

    return False


# Write your function here!


# Below are lines of code that create a linked list,
# and then search for two values in that linked list:
# one that is there, one that isn't. If your function
# works, it should print True then False.
node_7 = LinkedListNode(5)
node_6 = LinkedListNode(2, node_7)
node_5 = LinkedListNode(9, node_6)
node_4 = LinkedListNode(1, node_5)
node_3 = LinkedListNode(4, node_4)
node_2 = LinkedListNode(6, node_3)
root_node = LinkedListNode(7, node_2)

print(linked_list_search(root_node, 9))
print(linked_list_search(root_node, 3))