添加0707.设计链表 Swift版本

problems/0707.设计链表.md

@@ -948,6 +948,87 @@ class MyLinkedList {
 }
 ```
 
+Swift:
+
+```swift
+class MyLinkedList {
+    var dummyHead: ListNode<Int>?
+    var size: Int
+    
+    init() {
+        dummyHead = ListNode(0)
+        size = 0
+    }
+    
+    func get(_ index: Int) -> Int {
+        if index >= size || index < 0 {
+            return -1
+        }
+        
+        var curNode = dummyHead?.next
+        var curIndex = index
+        
+        while curIndex > 0 {
+            curNode = curNode?.next
+            curIndex -= 1
+        }
+        
+        return curNode?.value ?? -1
+    }
+    
+    func addAtHead(_ val: Int) {
+        let newHead = ListNode(val)
+        newHead.next = dummyHead?.next
+        dummyHead?.next = newHead
+        size += 1
+    }
+    
+    func addAtTail(_ val: Int) {
+        let newNode = ListNode(val)
+        var curNode = dummyHead
+        while curNode?.next != nil {
+            curNode = curNode?.next
+        }
+        
+        curNode?.next = newNode
+        size += 1
+    }
+    
+    func addAtIndex(_ index: Int, _ val: Int) {
+        if index > size {
+            return
+        }
+        
+        let newNode = ListNode(val)
+        var curNode = dummyHead
+        var curIndex = index
+      
+        while curIndex > 0 {
+            curNode = curNode?.next
+            curIndex -= 1
+        }
+      
+        newNode.next = curNode?.next
+        curNode?.next = newNode
+        size += 1
+    }
+    
+    func deleteAtIndex(_ index: Int) {
+        if index >= size || index < 0 {
+            return
+        }
+        
+        var curNode = dummyHead
+        for _ in 0..<index {
+            curNode = curNode?.next
+        }
+        
+        curNode?.next = curNode?.next?.next
+        size -= 1
+    }
+}
+```
+
 
 
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