Reverse Linked List

Reverse a singly linked list.

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Hint:

A linked list can be reversed either iteratively or recursively. Could you implement both?

iteratively:

1 /**2 * Definition for singly-linked list.3 * public class ListNode {4 * int val;5 * ListNode Next;6 * ListNode (int x) {val = x;}7  * }8  */9  Public classSolution {Ten      PublicListNode reverselist (ListNode head) { OneListNode first =NULL; AListNode second =head; -          while(Second! =NULL){ -ListNode tmp =Second.next; theSecond.next =First ; -First =second; -Second =tmp; -         } +         returnFirst ; -     } +}

Recursively:

1 /**2 * Definition for singly-linked list.3 * public class ListNode {4 * int val;5 * ListNode Next;6 * ListNode (int x) {val = x;}7  * }8  */9  Public classSolution {Ten      PublicListNode reverselist (ListNode head) { One         if(Head = =NULL|| Head.next = =NULL)returnhead; AListNode NextNode =Head.next; -Head.next =NULL; -ListNode Newhead =reverselist (nextnode); theNextnode.next =head; -         returnNewhead; -     } -}

Reverse Linked List