Update 0019.删除链表的倒数第N个节点.md

problems/0019.删除链表的倒数第N个节点.md

@@ -127,21 +127,29 @@ Python:
 #     def __init__(self, val=0, next=None):
 #         self.val = val
 #         self.next = next
+
 class Solution:
     def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
-        head_dummy = ListNode()
-        head_dummy.next = head
+        # 创建一个虚拟节点，并将其下一个指针设置为链表的头部
+        dummy_head = ListNode(0, head)
         
-        slow, fast = head_dummy, head_dummy
-        while(n>=0): #fast先往前走n+1步
+        # 创建两个指针，慢指针和快指针，并将它们初始化为虚拟节点
+        slow = fast = dummy_head
+        
+        # 快指针比慢指针快 n+1 步
+        for i in range(n+1):
             fast = fast.next
-            n -= 1
-        while(fast!=None):
+        
+        # 移动两个指针，直到快速指针到达链表的末尾
+        while fast:
             slow = slow.next
             fast = fast.next
-        #fast 走到结尾后，slow的下一个节点为倒数第N个节点
-        slow.next = slow.next.next #删除
-        return head_dummy.next
+        
+        # 通过更新第 (n-1) 个节点的 next 指针删除第 n 个节点
+        slow.next = slow.next.next
+        
+        return dummy_head.next
+
 ```
 Go:
 ```Go