lintcode-easy-Reverse Linked List

Posted 2020-06-18 哥布林工程师

Reverse a linked list.

For linked list 1->2->3, the reversed linked list is 3->2->1

/**
 * Definition for ListNode.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int val) {
 *         this.val = val;
 *         this.next = null;
 *     }
 * }
 */ 
public class Solution {
    /**
     * @param head: The head of linked list.
     * @return: The new head of reversed linked list.
     */
    public ListNode reverse(ListNode head) {
        // write your code here
        if(head == null || head.next == null)
            return head;
        
        ListNode prev = null;
        ListNode curr = head;
        ListNode next = head.next;
        
        while(next != null){
            curr.next = prev;
            prev = curr;
            curr = next;
            next = next.next;
        }
        curr.next = prev;
        
        return curr;
    }
}