What is XOR Linked list and its benefit ?

XOR Linked list is the memory efficient version of Doubly Linked list.

An ordinary Doubly Linked list needs 2 pointers - for next and previous elements.
XOR Linked list uses bitwise XOR operation to save the space (Keeps single pointer with XOR of both the pointers instead of 2 pointers)

EXAMPLE
Node1 : npx = 0 XOR pointer(Node1)
Node2 : npx = pointer(Node1) XOR pointer(Node2)
Node3 : npx = pointer(Node2) XOR pointer(Node3)
Node4 : npx = pointer(Node3) XOR 0