解题思路1:
链表的长度len
删除链表的倒数第N个结点就是删除链表的第len - N个结点
```java
class Solution {
public ListNode removeNthFromEnd(ListNode head, int n) {
ListNode tmp = new ListNode(0, head);
int len = 0;
while(tmp.next != null){
len++;
tmp = tmp.next;
}
ListNode node = new ListNode(0, head);
int count = 1;
while(true){
if(n == len){
node.next = head.next;
break;
}else if(count == len - n){
head.next = head.next.next;
break;
}
head = head.next;
count++;
}
return node.next;
}
}
解题思路2:
利用栈先进后出
class Solution {
public ListNode removeNthFromEnd(ListNode head, int n) {
ListNode dummy = new ListNode(0, head);
Deque<ListNode> stack = new LinkedList<>();
ListNode cur = dummy;
while(cur != null){
stack.push(cur);
cur = cur.next;
}
for(int i = 0; i < n; i++){
stack.pop();
}
ListNode pre = stack.peek();
pre.next = pre.next.next;
return dummy.next;
}
}
