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chore: copy the same problem solutions from lc to lcof2: No.021,022,023
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‎lcof2/剑指 Offer II 021. 删除链表的倒数第 n 个结点/README.md‎

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<!-- 这里可写通用的实现逻辑 -->
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利用快慢指针和虚拟头节点
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<!-- tabs:start -->
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### **Python3**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```python
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# Definition for singly-linked list.
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# class ListNode:
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# def __init__(self, val=0, next=None):
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# self.val = val
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# self.next = next
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class Solution:
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def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
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dummy = ListNode(next=head)
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slow, fast = dummy, dummy
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for _ in range(n):
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fast = fast.next
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while fast.next:
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slow = slow.next
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fast = fast.next
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slow.next = slow.next.next
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return dummy.next
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```
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### **Java**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```java
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/**
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* Definition for singly-linked list.
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* public class ListNode {
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* int val;
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* ListNode next;
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* ListNode() {}
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* ListNode(int val) { this.val = val; }
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* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
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* }
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*/
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class Solution {
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public ListNode removeNthFromEnd(ListNode head, int n) {
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ListNode dummy = new ListNode(0, head);
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ListNode fast = dummy, slow = dummy;
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while (n-- > 0) {
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fast = fast.next;
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}
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while (fast.next != null) {
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slow = slow.next;
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fast = fast.next;
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}
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slow.next = slow.next.next;
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return dummy.next;
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}
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}
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```
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### **C++**
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```cpp
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/**
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* Definition for singly-linked list.
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* struct ListNode {
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* int val;
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* ListNode *next;
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* ListNode() : val(0), next(nullptr) {}
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* ListNode(int x) : val(x), next(nullptr) {}
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* ListNode(int x, ListNode *next) : val(x), next(next) {}
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* };
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*/
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class Solution {
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public:
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ListNode* removeNthFromEnd(ListNode* head, int n) {
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ListNode* dummy = new ListNode(0, head);
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ListNode* fast = dummy;
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ListNode* slow = dummy;
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while (n--) {
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fast = fast->next;
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}
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while (fast->next) {
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slow = slow->next;
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fast = fast->next;
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}
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slow->next = slow->next->next;
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return dummy->next;
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}
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};
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```
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### **Go**
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```go
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/**
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* Definition for singly-linked list.
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* type ListNode struct {
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* Val int
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* Next *ListNode
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* }
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*/
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func removeNthFromEnd(head *ListNode, n int) *ListNode {
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dummy := &ListNode{0, head}
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fast := dummy
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slow := dummy
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for n > 0 {
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fast = fast.Next
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n -= 1
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}
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for fast.Next != nil {
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slow = slow.Next
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fast = fast.Next
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}
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slow.Next = slow.Next.Next
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return dummy.Next
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}
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```
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### **JavaScript**
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```js
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/**
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* Definition for singly-linked list.
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* function ListNode(val, next) {
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* this.val = (val===undefined ? 0 : val)
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* this.next = (next===undefined ? null : next)
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* }
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*/
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/**
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* @param {ListNode} head
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* @param {number} n
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* @return {ListNode}
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*/
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var removeNthFromEnd = function(head, n) {
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const dummy = new ListNode(0, head);
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let fast = dummy, slow = dummy;
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while (n--) {
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fast = fast.next;
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}
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while (fast.next) {
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slow = slow.next;
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fast = fast.next;
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}
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slow.next = slow.next.next;
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return dummy.next;
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};
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```
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### **Ruby**
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```rb
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# Definition for singly-linked list.
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# class ListNode
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# attr_accessor :val, :next
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# def initialize(val = 0, _next = nil)
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# @val = val
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# @next = _next
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# end
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# end
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# @param {ListNode} head
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# @param {Integer} n
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# @return {ListNode}
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def remove_nth_from_end(head, n)
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dummy = ListNode.new(0, head)
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fast = slow = dummy
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while n > 0
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fast = fast.next
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n -= 1
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end
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while fast.next
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slow = slow.next
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fast = fast.next
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end
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slow.next = slow.next.next
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return dummy.next
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end
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```
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### **...**

‎lcof2/剑指 Offer II 021. 删除链表的倒数第 n 个结点/Solution.cpp‎

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/**
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* Definition for singly-linked list.
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* struct ListNode {
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* int val;
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* ListNode *next;
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* ListNode() : val(0), next(nullptr) {}
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* ListNode(int x) : val(x), next(nullptr) {}
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* ListNode(int x, ListNode *next) : val(x), next(next) {}
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* };
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*/
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class Solution {
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public:
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ListNode* removeNthFromEnd(ListNode* head, int n) {
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ListNode* dummy = new ListNode(0, head);
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ListNode* fast = dummy;
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ListNode* slow = dummy;
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while (n--) {
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fast = fast->next;
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}
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while (fast->next) {
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slow = slow->next;
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fast = fast->next;
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}
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slow->next = slow->next->next;
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return dummy->next;
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}
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};

‎lcof2/剑指 Offer II 021. 删除链表的倒数第 n 个结点/Solution.go‎

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/**
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* Definition for singly-linked list.
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* type ListNode struct {
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* Val int
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* Next *ListNode
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* }
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*/
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func removeNthFromEnd(head *ListNode, n int) *ListNode {
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dummy := &ListNode{0, head}
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fast := dummy
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slow := dummy
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for n > 0 {
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fast = fast.Next
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n -= 1
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}
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for fast.Next != nil {
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slow = slow.Next
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fast = fast.Next
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}
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slow.Next = slow.Next.Next
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return dummy.Next
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}

‎lcof2/剑指 Offer II 021. 删除链表的倒数第 n 个结点/Solution.java‎

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
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/**
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* Definition for singly-linked list.
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* public class ListNode {
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* int val;
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* ListNode next;
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* ListNode() {}
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* ListNode(int val) { this.val = val; }
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* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
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* }
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*/
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class Solution {
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public ListNode removeNthFromEnd(ListNode head, int n) {
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ListNode dummy = new ListNode(0, head);
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ListNode fast = dummy, slow = dummy;
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while (n-- > 0) {
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fast = fast.next;
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}
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while (fast.next != null) {
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slow = slow.next;
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fast = fast.next;
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}
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slow.next = slow.next.next;
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return dummy.next;
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}
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}

‎lcof2/剑指 Offer II 021. 删除链表的倒数第 n 个结点/Solution.js‎

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
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/**
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* Definition for singly-linked list.
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* function ListNode(val, next) {
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* this.val = (val===undefined ? 0 : val)
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* this.next = (next===undefined ? null : next)
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* }
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*/
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/**
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* @param {ListNode} head
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* @param {number} n
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* @return {ListNode}
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*/
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var removeNthFromEnd = function(head, n) {
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const dummy = new ListNode(0, head);
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let fast = dummy, slow = dummy;
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while (n--) {
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fast = fast.next;
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}
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while (fast.next) {
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slow = slow.next;
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fast = fast.next;
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}
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slow.next = slow.next.next;
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return dummy.next;
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};

‎lcof2/剑指 Offer II 021. 删除链表的倒数第 n 个结点/Solution.py‎

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# Definition for singly-linked list.
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# class ListNode:
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# def __init__(self, val=0, next=None):
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# self.val = val
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# self.next = next
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class Solution:
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def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
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dummy = ListNode(next=head)
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slow, fast = dummy, dummy
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for _ in range(n):
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fast = fast.next
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while fast.next:
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slow = slow.next
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fast = fast.next
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slow.next = slow.next.next
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return dummy.next

‎lcof2/剑指 Offer II 021. 删除链表的倒数第 n 个结点/Solution.rb‎

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
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# Definition for singly-linked list.
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# class ListNode
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# attr_accessor :val, :next
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# def initialize(val = 0, _next = nil)
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# @val = val
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# @next = _next
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# end
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# end
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# @param {ListNode} head
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# @param {Integer} n
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# @return {ListNode}
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def remove_nth_from_end(head, n)
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dummy = ListNode.new(0, head)
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fast = slow = dummy
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while n > 0
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fast = fast.next
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n -= 1
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end
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while fast.next
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slow = slow.next
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fast = fast.next
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end
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slow.next = slow.next.next
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return dummy.next
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end

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