逆序访问单链表

This is a simple but important algorithm when dealing with singly linked list.

This algorithms can reversely access a singly linked list using O(n) time. Below is my code in Java.

class Node{

    Node next;

    int val;

}



class SinglyLinkedList{

    

    Node head;

    Node tail;

    

    //append a new Node to tail

    void append(Node nd){

        

        //head and tail must both be null or both be not null

        if(head == null && tail == null){

            head = nd;

            tail = nd;

            

        }else{

            tail.next = nd;

            tail = nd;

        }

    }



    void print(){

        Node temp = head;

        while(temp != null){

            System.out.print(temp.val + " ");

            temp = temp.next;

        }

    }

    

    void printInReverseOrder(){

        printInReverseOrder_General(head);

    }



    void printInReverseOrder_General(Node from){

        if(from == null){

            return;

        }

        Node temp = from;

        

        printInReverseOrder_General(temp.next);

        System.out.print(temp.val + " ");

        

    }

}