Question

• Insert: this method takes a value as a parameter and adds a node which contains the value to the end of the linked list

• Delete: This method deletes a node from the linked list. If an index is passed as a parameter, then the method should delete the node at this index. If no index is passed, then delete the first item in the list

• Find: this method takes a value as a parameter, and returns the index of the first node which contains this value. If no nodes are found to contain this value, return False

• Reverse: this method reverses the Linked List

• Do not edit Lab5.py except to complete the methods required, and to add your name and student number at the top of the file. Any adjustments to the file outside of these will result in grades being deducted.

  You do not need to concern yourself with error handling. For example, you can assume that when delete is called, it is called with an appropriate index.

class Node:

    def __init__(self, dataval=None):

        self.dataval = dataval

        self.nextval = None

class LinkedList:

    def __init__(self):

        self.headval = None

    def __str__(self):

        node = self.headval

        output = "[ "

        while(node != None):

            output = output + str(node.dataval) + ", "

            node = node.nextval

        if(len(output) > 2):

            output = output[:-2]

        return output + " ]"

# DO NOT EDIT ANY CODE ABOVE THIS LINE

    def insert(self, val):

        # Fill in this method, which takes a value and adds a node which holds the value at the end of the linked list

    def delete(self, index=0):

        # Fill in this method, which takes an index(with a default value of 0), and deletes the node at the index specified

    def find(self, val):

        # Fill in this method, which takes in a value and returns the index of the first node which contains that value. If no node containing that value is found, return False

    def reverse(self):

        # Fill in this method, which reverses the list

#DO NOT EDIT ANY CODE PAST THIS LINE

# Tests

# Insertion

a = LinkedList()

a.insert(1)

a.insert(2)

a.insert('a')

a.insert(3)

print(str(a) == "[ 1, 2, a, 3 ]")

# Deletion

a.delete()

print(str(a) == "[ 2, a, 3 ]")

a.delete(2)

print(str(a) == "[ 2, a ]")

# Find

a.insert('b')

a.insert('c')

a.insert('b')

print(a.find('b') == 2)

print(a.find('c') == 3)

print(a.find('d') == False)

# Reverse

a.reverse()

print(str(a) == "[ b, c, b, a, 2 ]")

Answer 1

Program

Text format:

class Node:
    def __init__(self, dataval=None):
        self.dataval = dataval
        self.nextval = None


class LinkedList:
    def __init__(self):
        self.headval = None

    def __str__(self):
        node = self.headval
        output = "[ "
        while (node != None):
            output = output + str(node.dataval) + ", "
            node = node.nextval
        if (len(output) > 2):
            output = output[:-2]
        return output + " ]"

    # DO NOT EDIT ANY CODE ABOVE THIS LINE

    def insert(self, val):
        # Fill in this method, which takes a value and adds a node which holds the value at the end of the linked list
        new_node = Node(val)
        if self.headval is None:
            self.headval = new_node
        else:
            cur = self.headval
            while cur.nextval is not None:
                cur = cur.nextval
            cur.nextval = new_node

    def delete(self, index=0):
        # Fill in this method, which takes an index(with a default value of 0), and deletes the node at the index specified
        if index == 0:
            self.headval = self.headval.nextval
        else:
            cur = self.headval
            pre = None
            for i in range(index):
                pre = cur
                cur = cur.nextval
            pre.nextval = cur.nextval

    def find(self, val):
        # Fill in this method, which takes in a value and returns the index of the first node which contains that value. If no node containing that value is found, return False
        cur = self.headval
        index = 0
        while cur!= None and cur.dataval != val:
            cur = cur.nextval
            index += 1
        if cur != None:
            return index
        return False

    def reverse(self):
        # Fill in this method, which reverses the list
        prev = None
        cur = self.headval
        while cur is not None:
            next = cur.nextval
            cur.nextval = prev
            prev = cur
            cur = next
        self.headval = prev


# DO NOT EDIT ANY CODE PAST THIS LINE

# Tests

# Insertion
a = LinkedList()
a.insert(1)
a.insert(2)
a.insert('a')
a.insert(3)
print(str(a) == "[ 1, 2, a, 3 ]")

# Deletion
a.delete()
print(str(a) == "[ 2, a, 3 ]")
a.delete(2)
print(str(a) == "[ 2, a ]")

# Find
a.insert('b')
a.insert('c')
a.insert('b')
print(a.find('b') == 2)
print(a.find('c') == 3)
print(a.find('d') == False)

# Reverse
a.reverse()
print(str(a) == "[ b, c, b, a, 2 ]")


Output:

True
True
True
True
True
True
True

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