Doubly Linked Lists.md

https://visualgo.net/en/list

Doubly linked lists are a collection of nodes that point to two other nodes or null. These nodes have three elements which are the value it contains, a pointer to the next node, and another pointer to the previous node. Doubly linked lists are null terminated meaning that the the first and last nodes, or the head and tail pointers, point to a null value.

	   [head]      [value]     [value]     [value]     [tail]
	   [pointer] > [pointer] > [pointer] > [pointer] > [pointer] > null
null < [pointer] < [pointer] < [pointer] < [pointer] < [pointer]

Method	[[Big O]]
getNth	O(n)
addFirst	O(1)
addEnd	O(1)
remove	O(n)

 public class DoubleListNode {
 
	int val;

	ListNode next;
	ListNode last;

	ListNode() {}
      
	ListNode(int val) {
		this.val = val;
	}
      
	ListNode(int val, ListNode next, ListNode last) {
		this.val = val;
		this.next = next;
		this.last = last;
	}
	
}