206. Reverse Linked List

Reverse a singly linked list.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode reverseList(ListNode head) {
        if(head==null||head.next==null) return head;
        ListNode A= head, B=A.next, C = B.next;
        while(B!=null){
            C=B.next;
            B.next=A;
            A=B;
            B=C;
        }
        head.next = null;
        return A;
    }
}