Problem Challenge 2

We'll cover the following

- - Rearrange a LinkedList (medium)
  - Try it yourself

Rearrange a LinkedList (medium) #

Given the head of a Singly LinkedList, write a method to modify the LinkedList such that the nodes from the second half of the LinkedList are inserted alternately to the nodes from the first half in reverse order. So if the LinkedList has nodes 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> null, your method should return 1 -> 6 -> 2 -> 5 -> 3 -> 4 -> null.

Your algorithm should not use any extra space and the input LinkedList should be modified in-place.

Example 1:

Input: 2 -> 4 -> 6 -> 8 -> 10 -> 12 -> null
Output: 2 -> 12 -> 4 -> 10 -> 6 -> 8 -> null

Example 2:

Input: 2 -> 4 -> 6 -> 8 -> 10 -> null
Output: 2 -> 10 -> 4 -> 8 -> 6 -> null

Try it yourself #

Try solving this question here:

Java

Python3

C++

from __future__ import print_function
 
 
class Node:
  def __init__(self, value, next=None):
    self.value = value
    self.next = next
 
  def print_list(self):
    temp = self
    while temp is not None:
      print(str(temp.value) + " ", end='')
      temp = temp.next
    print()
 
 
def reorder(head):
  # TODO: Write your code here
  return
 
 
def main():
  head = Node(2)
  head.next = Node(4)
  head.next.next = Node(6)
  head.next.next.next = Node(8)
  head.next.next.next.next = Node(10)
  head.next.next.next.next.next = Node(12)
  reorder(head)
  head.print_list()
 
 
main()
 

Output

0.462s

2 4 6 8 10 12

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Solution Review: Problem Challenge 2