Python Program To Delete Middle Of Linked List

# Python3 program to delete middle
# of a linked list
 
# Link list Node 
class Node:    
    def __init__(self):        
        self.data = 0
        self.next = None
    
# Count of nodes
def countOfNodes(head):
    count = 0    
    while (head != None):
        head = head.next
        count += 1
    
    return count

# Deletes middle node and returns
# head of the modified list
def deleteMid(head):

    # Base cases
    if (head == None):
        return None
    if (head.next == None):
        del head
        return None

    copyHead = head
 
    # Find the count of nodes
    count = countOfNodes(head)
 
    # Find the middle node
    mid = count // 2
 
    # Delete the middle node
    while (mid > 1):
        mid -= 1
        head = head.next
 
    # Delete the middle node
    head.next = head.next.next
 
    return copyHead

# A utility function to print
# a given linked list
def printList(ptr):
    while (ptr != None):
        print(ptr.data, 
              end = '->')
        ptr = ptr.next
    
    print('NULL')
    
# Utility function to create 
# a new node.
def newNode(data):
    temp = Node()
    temp.data = data
    temp.next = None
    return temp

# Driver Code
if __name__=='__main__':
    
    # Start with the empty list
    head = newNode(1)
    head.next = newNode(2)
    head.next.next = newNode(3)
    head.next.next.next = newNode(4)
 
    print("Given Linked List")
    printList(head)
 
    head = deleteMid(head)
 
    print("Linked List after deletion of middle")
    printList(head)

# This code is contributed by rutvik_56

# Python3 program to delete the
# middle of a linked list

# Linked List Node
class Node:    
    def __init__(self, data):
        self.data = data
        self.next = None

# Create and handle list 
# operations
class LinkedList:    
    def __init__(self):
        
        # Head of the list
        self.head = None 

    # Add new node to the list end
    def addToList(self, data):        
        newNode = Node(data)
        if self.head is None:
            self.head = newNode
            return
            
        last = self.head
        
        while last.next:
            last = last.next
            
        last.next = newNode

    # Returns the list in string 
    # format
    def __str__(self):        
        linkedListStr = ""
        temp = self.head
        
        while temp:
            linkedListStr += str(temp.data) + "->"
            temp = temp.next
            
        return linkedListStr + "NULL"

    # Method deletes middle node
    def deleteMid(self):

        # Base cases
        if (self.head is None or 
            self.head.next is None):
            return

        # Initialize slow and fast pointers
        # to reach middle of linked list
        slow_Ptr = self.head
        fast_Ptr = self.head

        # Find the middle and previous of 
        # middle
        prev = None

        # To store previous of slow pointer
        while (fast_Ptr is not None and 
               fast_Ptr.next is not None):
            fast_Ptr = fast_Ptr.next.next
            prev = slow_Ptr
            slow_Ptr = slow_Ptr.next

        # Delete the middle node
        prev.next = slow_Ptr.next

# Driver code
linkedList = LinkedList()

linkedList.addToList(1)
linkedList.addToList(2)
linkedList.addToList(3)
linkedList.addToList(4)

print("Given Linked List")
print(linkedList)

linkedList.deleteMid()

print("Linked List after deletion of middle")
print(linkedList)
# This code is contributed by Debidutta Rath