Python Program For Inserting Node In The Middle Of The Linked List

# Python3 implementation to insert node
# at the middle of a linked list

# Node class
class Node:

    # constructor to create a new node
    def __init__(self, data):
        self.data = data
        self.next = None

# function to insert node at the
# middle of linked list given the head
def insertAtMid(head, x):

    if(head == None): #if the list is empty
        head = Node(x)
    else:
        
        # create a new node for the value
        # to be inserted
        newNode = Node(x)

        ptr = head
        length = 0
        
        # calculate the length of the linked
        # list
        while(ptr != None):
            ptr = ptr.next
            length += 1

        # 'count' the number of node after which
        # the new node has to be inserted
        if(length % 2 == 0):
            count = length / 2 
        else:
            (length + 1) / 2

        ptr = head

        # move ptr to the node after which
        # the new node has to inserted
        while(count > 1):
            count -= 1
            ptr = ptr.next

        # insert the 'newNode' and adjust
        # links accordingly
        newNode.next = ptr.next
        ptr.next = newNode

# function to display the linked list
def display(head):
    temp = head
    while(temp != None):
        print(str(temp.data), end = " ")
        temp = temp.next

# Driver Code

# Creating the linked list 1.2.4.5
head = Node(1)
head.next = Node(2)
head.next.next = Node(4)
head.next.next.next = Node(5)

print("Linked list before insertion: ", end = "")
display(head)

# inserting 3 in the middle of the linked list.
x = 3
insertAtMid(head, x)

print("
Linked list after insertion: " , end = "")
display(head)

# This code is contributed by Pranav Devarakonda

# Python implementation to insert node 
# at the middle of the linked list 

# Node Class
class Node :
    def __init__(self, d):
        self.data = d 
        self.next = None
        
class LinkedList: 

    # function to insert node at the 
    # middle of the linked list
    def __init__(self):
        self.head = None
    
    # Function to insert a new node 
    # at the beginning 
    def push(self, new_data): 
        new_node = Node(new_data) 
        new_node.next = self.head 
        self.head = new_node 
        
    def insertAtMid(self, x):
        
        # if list is empty 
        if (self.head == None): 
            self.head = Node(x) 

        else: 
            
            # get a new node 
            newNode = Node(x) 

            # assign values to the slow 
            # and fast pointers 
            slow = self.head
            fast = self.head.next

            while (fast != None and 
                   fast.next != None): 
                
                # move slow pointer to next node 
                slow = slow.next

                # move fast pointer two nodes 
                # at a time 
                fast = fast.next.next

            # insert the 'newNode' and 
            # adjust the required links 
            newNode.next = slow.next
            slow.next = newNode

    # function to display the linked list 
    def display(self):
        temp = self.head 
        while (temp != None): 
            print(temp.data, end = " "),
            temp = temp.next

# Driver Code

# Creating the list 1.2.4.5 
ll = LinkedList()
ll.push(5)
ll.push(4)
ll.push(2)
ll.push(1)
print("Linked list before insertion: "),
ll.display()

x = 3
ll.insertAtMid(x)

print("
Linked list after insertion: "),
ll.display()

# This code is contributed by prerna saini