题目描述

给定一个链表，删除链表的倒数第 n 个结点，并且返回链表的头结点。

提示：

• 链表中结点的数目为 sz
• 1 <= sz <= 30
• 0 <= Node.val <= 100
• 1 <= n <= sz

测试用例

• 输入：head = [1,2,3,4,5], n = 2
• 输出：[1,2,3,5]

代码实现

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} n
 * @return {ListNode}
 */
var removeNthFromEnd = function(head, n) {
    // 快慢指针
    let dmy = new ListNode(-1, head);
    let fast = dmy;
    let slow = dmy;

    while(n){
        fast = fast.next;
        n --;
    }
    while(fast && fast.next){
        fast = fast.next;
        slow = slow.next;
    }
    slow.next = slow.next.next;
    return dmy.next;
};