Merge pull request #2458 from lavaicer/master

优化 19. 删除链表的倒数第 N 个结点 go 代码

problems/0019.删除链表的倒数第N个节点.md

@@ -165,20 +165,17 @@ class Solution:
  * }
  */
 func removeNthFromEnd(head *ListNode, n int) *ListNode {
-    dummyHead := &ListNode{}
-    dummyHead.Next = head
-    cur := head
-    prev := dummyHead
-    i := 1
-    for cur != nil {
-        cur = cur.Next
-        if i > n {
-            prev = prev.Next
-        }
-        i++
-    }
-    prev.Next = prev.Next.Next
-    return dummyHead.Next
+	dummyNode := &ListNode{0, head}
+	fast, slow := dummyNode, dummyNode
+	for i := 0; i <= n; i++ { // 注意<=，否则快指针为空时，慢指针正好在倒数第n个上面
+		fast = fast.Next
+	}
+	for fast != nil {
+		fast = fast.Next
+		slow = slow.Next
+	}
+	slow.Next = slow.Next.Next
+	return dummyNode.Next
 }
 ```