[Swift]LeetCode203. 移除鏈表元素 | Remove Linked List Elements

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➤微信公衆號：山青詠芝（shanqingyongzhi）
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➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：http://www.javashuo.com/article/p-bsdietxk-md.html 
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Remove all elements from a linked list of integers that have value val.

Example:

Input:  1->2->6->3->4->5->6, val = 6
Output: 1->2->3->4->5

---

刪除鏈表中等於給定值 val 的全部節點。

示例:

輸入: 1->2->6->3->4->5->6, val = 6
輸出: 1->2->3->4->5

---

72ms

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     public var val: Int
 5  *     public var next: ListNode?
 6  *     public init(_ val: Int) {
 7  *         self.val = val
 8  *         self.next = nil
 9  *     }
10  * }
11  */
12 class Solution {
13     func removeElements(_ head: ListNode?, _ val: Int) -> ListNode? {
14         guard head != nil else { return nil }
15         
16         var head = head
17         while head != nil, head!.val == val {
18             head = head?.next
19         }
20         
21         var prev = head
22         var current = head?.next
23         
24         while let curr = current {
25             if curr.val == val {
26                 prev?.next = curr.next
27                 current = curr.next
28                 continue
29             }
30             prev = curr
31             current = curr.next
32         }
33         
34         return head
35     }
36 }

---

76ms

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     public var val: Int
 5  *     public var next: ListNode?
 6  *     public init(_ val: Int) {
 7  *         self.val = val
 8  *         self.next = nil
 9  *     }
10  * }
11  */
12 class Solution {
13     func removeElements(_ head: ListNode?, _ val: Int) -> ListNode? {
14         guard let head = head else { return nil }
15         head.next = removeElements(head.next, val)
16         return head.val == val ? head.next : head
17     }
18 }

---

80ms

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     public var val: Int
 5  *     public var next: ListNode?
 6  *     public init(_ val: Int) {
 7  *         self.val = val
 8  *         self.next = nil
 9  *     }
10  * }
11  */
12 class Solution {
13     func removeElements(_ head: ListNode?, _ val: Int) -> ListNode? {
14 
15         var dummy = ListNode(-1)
16         dummy.next = head
17         var cur = dummy
18         while cur.next != nil {
19             if cur.next!.val == val {
20                 cur.next = cur.next!.next
21             }
22             else{
23                 cur = cur.next!
24             }
25         }
26         return dummy.next
27     }
28 }

---

96ms

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     public var val: Int
 5  *     public var next: ListNode?
 6  *     public init(_ val: Int) {
 7  *         self.val = val
 8  *         self.next = nil
 9  *     }
10  * }
11  */
12 
13 class Solution {
14     func removeElements(_ head: ListNode?, _ val: Int) -> ListNode? {
15         guard let _ = head else {
16             return nil
17         }
18         
19         //在表頭添加一個哨兵節點
20         let fakeNode = ListNode(NSNotFound)
21         fakeNode.next = head
22         var prev:ListNode = fakeNode
23         var current:ListNode? = head
24         while let tmp = current {
25             if tmp.val != val {
26                 prev.next = tmp
27                 prev = prev.next!
28             }
29             current = tmp.next
30         }
31         
32         if prev.next != nil {
33             prev.next = nil
34         }
35         return fakeNode.next
36     }
37 }