LeetCode删除链表中倒数第n个结点

Given a linked list, remove the n-th node from the end of list and return its head.

Example:

Given linked list: 1->2->3->4->5, and n = 2.

After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:

Given n will always be valid.

class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode a = head;
        ListNode b = head;
        ListNode c = head;
        for(int i=0; i<n; i++){
            b = b.next;
        }
        if(b == null){
            return a.next;
        }
        while(b.next != null){
            b = b.next;
            c = c.next;
        }
        if(c.next.next == null){
            c.next = null;
        }else{
            c.next = c.next.next;
        }
        
        return a;
    }
}