Python Program For Arranging Single Linked List In Alternate Odd and Even Nodes Order

# Python program to rearrange nodes
# as alternate odd even nodes in
# a Singly Linked List

# Link list node 
class Node:     
    def __init__(self, data): 
        self.data = data 
        self.next = next
        
# A utility function to print
# linked list
def printList( node):
    while (node != None) :
        print(node.data , 
              end = " ")
        node = node.next
    
    print("")

# Function to create newNode
# in a linkedlist
def newNode(key):
    temp = Node(0)
    temp.data = key
    temp.next = None
    return temp

# Function to insert at beginning
def insertBeg(head, val):
    temp = newNode(val)
    temp.next = head
    head = temp
    return head

# Function to rearrange the
# odd and even nodes
def rearrangeOddEven(head):
    odd = []
    even = []
    i = 1

    while (head != None): 
        if (head.data % 2 != 0 and 
            i % 2 == 0):

            # Odd Value in Even Position
            # Add pointer to current node
            # in odd stack
            odd.append(head)
        
        elif (head.data % 2 == 0 and 
              i % 2 != 0): 

            # Even Value in Odd Position
            # Add pointer to current node
            # in even stack
            even.append(head)

        head = head.next
        i = i + 1

    while (len(odd) != 0 and 
           len(even) != 0) :

        # Swap Data at the top of two stacks
        odd[-1].data, even[-1].data = even[-1].data, odd[-1].data
        odd.pop()
        even.pop()
    
    return head

# Driver code
head = newNode(8)
head = insertBeg(head, 7)
head = insertBeg(head, 6)
head = insertBeg(head, 5)
head = insertBeg(head, 3)
head = insertBeg(head, 2)
head = insertBeg(head, 1)

print("Linked List:")
printList(head)
rearrangeOddEven(head)

print("Linked List after ", "Rearranging:")
printList(head)
# This code is contributed by Arnab Kundu

# Python3 program to rearrange nodes 
# as alternate odd even nodes in 
# a Singly Linked List 

# Structure node 
class Node :
    def __init__(self):
        self.data = 0
        self.next = None

# A utility function to print 
# linked list 
def printList(node) :
    while (node != None) :
        print(node.data, 
              end = " ") 
        node = node.next
    
    print(" ")

# Function to create newNode 
# in a linkedlist 
def newNode(key) :
    temp = Node() 
    temp.data = key 
    temp.next = None
    return temp 

# Function to insert at beginning 
def insertBeg(head, val) :
    temp = newNode(val) 
    temp.next = head 
    head = temp 
    return head 

# Function to rearrange the 
# odd and even nodes 
def rearrange(head) :

    # Step 1: Segregate even and odd nodes 
    # Step 2: Split odd and even lists 
    # Step 3: Merge even list into odd list 
    even = None
    temp = None
    prev_temp = None
    i = None
    j = None
    k = None
    l = None
    ptr = None

    # Step 1: Segregate Odd and Even Nodes 
    temp = (head).next
    prev_temp = head 

    while (temp != None) :
    
        # Backup next pointer of temp 
        x = temp.next

        # If temp is odd move the node 
        # to beginning of list 
        if (temp.data % 2 != 0) :        
            prev_temp.next = x 
            temp.next = (head) 
            (head) = temp 
        
        else:        
            prev_temp = temp 
        
        # Advance Temp Pointer 
        temp = x 
    
    # Step 2 
    # Split the List into Odd and even 
    temp = (head).next
    prev_temp = (head) 

    while (temp != None and 
           temp.data % 2 != 0) :
        prev_temp = temp 
        temp = temp.next
    
    even = temp 

    # End the odd List (Make last 
    # node None) 
    prev_temp.next = None

    # Step 3: 
    # Merge Even List into odd 
    i = head 
    j = even 

    while (j != None and 
           i != None):
    
        # While both lists are not 
        # exhausted Backup next 
        # pointers of i and j 
        k = i.next
        l = j.next

        i.next = j 
        j.next = k 

        # ptr points to the latest 
        # node added 
        ptr = j 

        # Advance i and j pointers 
        i = k 
        j = l 

    if (i == None):
    
        # Odd list exhausts before even, 
        # append remainder of even list to odd. 
        ptr.next = j 
        
    # The case where even list exhausts 
    # before odd list is automatically 
    # handled since we merge the even 
    # list into the odd list 
    return head

# Driver Code 
head = newNode(8) 
head = insertBeg(head, 7) 
head = insertBeg(head, 6) 
head = insertBeg(head, 3) 
head = insertBeg(head, 5) 
head = insertBeg(head, 1) 
head = insertBeg(head, 2) 
head = insertBeg(head, 10) 

print("Linked List:" ) 
printList(head) 
print("Rearranged List" ) 
head = rearrange(head) 
printList(head) 
# This code is contributed by Arnab Kundu