FW:Reverse a Singly Linked List Recursively in Java

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本文介绍了一种使用递归方法来反转单链表的方法。通过详细的步骤解析和Java代码实现，展示了如何处理边界条件，并提供了完整的代码示例。

http://www.technicalypto.com/2010/03/reverse-singly-linked-list-recursively.html

Reverse a Singly Linked List Recursively in Java

We have already seen how to reverse a singly linked list with illustrative pictures. Now lets see how we can do it recursively. In the previous problem we did it iteratively, now we shall do it recursively.
To attack any problem in a recursive approach, we need to be very clear about the end/boundary conditions. For a linked list, reverse of a null list or reverse of list of size 1 is going to be the same.
Reverse of a linked list of size x will be the reverse of the 'next' element followed by first.
A picture means a thousand words. So, here is what happens internally.

Now for the comprehensive Java code (reference for SinglyLinkedList implementation can be found here )

        package 
        dsa.linkedlist; 
       
        public 
        class 
        ReverseLinkedListRecursively { 
       
        public 
        static 
        void 
        main(String args[]){ 
       
        ReverseLinkedListRecursively reverser =  
        new 
        ReverseLinkedListRecursively(); 
       
        SinglyLinkedList<Integer> originalList = reverser.getLabRatList( 
        10 
        ); 
       
        System.out.println( 
        "Original List : " 
        +originalList.toString()); 
       
        originalList.start = reverser.reverse(originalList.start); 
       
        System.out.println( 
        "Reversed List : " 
        +originalList.toString()); 
       
        } 
       
        public 
        Node<Integer> reverse(Node<Integer> list) 
       
        { 
       
        if 
        (list ==  
        null 
        || list.next== 
        null 
        )  
        return 
        list; 
       
        Node<Integer> nextItem = list.next; 
       
        list.next =  
        null 
        ; 
       
        Node<Integer> reverseRest = reverse(nextItem); 
       
        nextItem.next = list; 
       
        return 
        reverseRest; 
       
        } 
       
        private 
        SinglyLinkedList<Integer> getLabRatList( 
        int 
        count){ 
       
        SinglyLinkedList<Integer> sampleList =  
        new 
        SinglyLinkedList<Integer>(); 
       
        for 
        ( 
        int 
        i= 
        0 
        ;i<count;i++){ 
       
        sampleList.add(i); 
       
        } 
       
        return 
        sampleList; 
       
        } 
       
        } 
       
        /* 
       
        * SAMPLE OUTPUT 
       
        * Original List : 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 
       
        * Reversed List : 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 
       
        */