题解 | #删除链表的倒数第n个节点#

这几个题用map来解都感觉变简单了，是不是属于逃课啊？

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param head ListNode类 
     * @param n int整型 
     * @return ListNode类
     */
    public ListNode removeNthFromEnd (ListNode head, int n) {
        // write code here
        ListNode newHead = head;
        if(head == null) return null;
        if(head.next == null) return null;
        HashMap<Integer, ListNode> map = new HashMap<>();
        int length = 0;
        for(int i = 0; head != null; head = head.next){
            map.put(i, head);
            length = i;
            i++;
        }
        if(length - n + 1 == 0) return newHead.next;
        ListNode pre = map.get(length - n);
        ListNode node = map.get(length - n + 1);
        pre.next = node.next;
        return newHead;
    }
}