题目

• 原题连接：19. 删除链表的倒数第 N 个结点

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1- 思路

模式识别：删除倒数第 n 个结点 ——> 定义 dummyHead 并用双指针实现删除逻辑

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2- 实现

⭐19. 删除链表的倒数第 N 个结点——题解思路

class Solution {public ListNode removeNthFromEnd(ListNode head, int n) {if(head==null){return head;}ListNode dummyHead = new ListNode(-1);dummyHead.next = head;ListNode fast = dummyHead;ListNode slow = dummyHead;for(int i = 0 ; i < n ; i++){fast = fast.next;}while(fast.next!=null){slow = slow.next;fast = fast.next;}slow.next = slow.next.next;return dummyHead.next;}
}

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3- ACM实现

public class removeLastN {static class ListNode{int val;ListNode next;ListNode(){}ListNode(int x){val = x;}}public static ListNode removeLast(ListNode head,int n ){// 双指针ListNode dummyHead = new ListNode(-1);dummyHead.next = head;ListNode slow = dummyHead;ListNode fast = dummyHead;for(int i = 0 ; i < n ;i++){fast = fast.next;}while(fast.next!=null){slow = slow.next;fast = fast.next;}slow.next = slow.next.next;return dummyHead.next;}public static void main(String[] args) {Scanner sc  = new Scanner(System.in);System.out.println("输入链表长度");int n = sc.nextInt();System.out.println("输入链表元素");ListNode head = null,tail = null;for(int i = 0 ; i < n;i++){ListNode newNode = new ListNode(sc.nextInt());if(head==null){head = newNode;tail = newNode;}else{tail.next = newNode;tail = newNode;}}System.out.println("输入删除倒数第几个元素");int k = sc.nextInt();ListNode Res = removeLast(head,k);while(Res!=null){System.out.print(Res.val+" ");Res = Res.next;}}
}

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