Merge pull request #615 from qxuewei/master

添加 203.移除链表元素 Swift版本

problems/0203.移除链表元素.md

@@ -304,8 +304,7 @@ var removeElements = function(head, val) {
 };
 ```
 
-Swift:
-
+Swift：
 ```swift
 /**
  * Definition for singly-linked list.

problems/0206.翻转链表.md

@@ -334,6 +334,43 @@ fun reverseList(head: ListNode?): ListNode? {
 }
 ```
 
+Swift：
+```swift
+/// 双指针法 (迭代)
+/// - Parameter head: 头结点
+/// - Returns: 翻转后的链表头结点
+func reverseList(_ head: ListNode?) -> ListNode? {
+    if head == nil || head?.next == nil {
+        return head
+    }
+    var pre: ListNode? = nil
+    var cur: ListNode? = head
+    var temp: ListNode? = nil
+    while cur != nil {
+        temp = cur?.next
+        cur?.next = pre
+        pre = cur
+        cur = temp
+    }
+    return pre
+}
+
+/// 递归
+/// - Parameter head: 头结点
+/// - Returns: 翻转后的链表头结点
+func reverseList2(_ head: ListNode?) -> ListNode? {
+    return reverse(pre: nil, cur: head)
+}
+func reverse(pre: ListNode?, cur: ListNode?) -> ListNode? {
+    if cur == nil {
+        return pre
+    }
+    let temp: ListNode? = cur?.next
+    cur?.next = pre
+    return reverse(pre: cur, cur: temp)
+}
+```
+
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)

problems/0707.设计链表.md

@@ -948,6 +948,70 @@ class MyLinkedList {
 }
 ```
 
+Swift
+```Swift
+class MyLinkedList {
+    var size = 0
+    let head: ListNode
+    
+    /** Initialize your data structure here. */
+    init() {
+        head = ListNode(-1)
+    }
+    
+    /** Get the value of the index-th node in the linked list. If the index is invalid, return -1. */
+    func get(_ index: Int) -> Int {
+        if size > 0 && index < size {
+            var tempHead = head
+            for _ in 0..<index {
+                tempHead = tempHead.next!
+            }
+            let currentNode = tempHead.next!
+            return currentNode.val
+        } else {
+            return -1
+        }
+    }
+    
+    /** Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list. */
+    func addAtHead(_ val: Int) {
+        addAtIndex(0, val)
+    }
+    
+    /** Append a node of value val to the last element of the linked list. */
+    func addAtTail(_ val: Int) {
+        addAtIndex(size, val)
+    }
+    
+    /** Add a node of value val before the index-th node in the linked list. If index equals to the length of linked list, the node will be appended to the end of linked list. If index is greater than the length, the node will not be inserted. */
+    func addAtIndex(_ index: Int, _ val: Int) {
+        if index > size {
+            return
+        }
+        let idx = (index >= 0 ? index : 0)
+        var tempHead = head
+        for _ in 0 ..< idx {
+            tempHead = tempHead.next!
+        }
+        let currentNode = tempHead.next
+        let newNode = ListNode(val, currentNode)
+        tempHead.next = newNode
+        size += 1
+    }
+    
+    /** Delete the index-th node in the linked list, if the index is valid. */
+    func deleteAtIndex(_ index: Int) {
+        if size > 0 && index < size {
+            var tempHead = head
+            for _ in 0 ..< index {
+                tempHead = tempHead.next!
+            }
+            tempHead.next = tempHead.next!.next
+            size -= 1
+        }
+    }
+}
+```
 
 
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