Swap Kth node from beginning with Kth node from end in a Linked List

Last Updated: 17–07–2020

Given a singly linked list, swap kth node from beginning with kth node from end. Swapping of data is not allowed, only pointers should be changed. This requirement may be logical in many situations where the linked list data part is huge (For example student details line Name, RollNo, Address, ..etc). The pointers are always fixed (4 bytes for most of the compilers).

Example:

Input: 1 -> 2 -> 3 -> 4 -> 5, K = 2
Output: 1 -> 4 -> 3 -> 2 -> 5 
Explanation: The 2nd node from 1st is 2 and 
2nd node from last is 4, so swap them.

Input: 1 -> 2 -> 3 -> 4 -> 5, K = 5
Output: 5 -> 2 -> 3 -> 4 -> 1 
Explanation: The 5th node from 1st is 5 and 
5th node from last is 1, so swap them.

code:

def get_length(self):
    temp = self.head
    count = 0
    if temp == None:
        return count
    while(temp):
        if temp.next == None:
            return count+1
        count+=1
        temp = temp.next
def swap(self,a,b = None):
    a=a-1
    if b == None:
        b=a
    temp = self.head
    length = self.get_length()
    for i in range(a):
        temp = temp.next
    a_val = temp.data
    temp = self.head
    for i in range(length-b-1):
        temp = temp.next
    b_val = temp.data
    temp.data = a_val
    temp = self.head
    for i in range(a):
        temp = temp.next
    temp.data = b_val
    return