为链表篇 增加 Swift 实现

animation-simulation/链表篇/leetcode147对链表进行插入排序.md

@@ -225,5 +225,41 @@ class Solution:
         return dummyNode.next
 ```
 
+Swift Code：
 
-
+```swift
+class Solution {
+    func insertionSortList(_ head: ListNode?) -> ListNode? {
+        if head == nil && head?.next == nil {
+            return head
+        }
+        //哑节点
+        var dummyNode = ListNode(-1)
+        dummyNode.next = head
+        //pre负责指向新元素，last 负责指向新元素的前一元素
+        //判断是否需要执行插入操作
+        var pre = head?.next
+        var last = head
+        while pre != nil {
+            //不需要插入到合适位置，则继续往下移动
+            if last!.val <= pre!.val {
+                pre = pre?.next
+                last = last?.next
+                continue
+            }
+            //开始出发，查找新元素的合适位置
+            var temphead = dummyNode
+            while temphead.next!.val <= pre!.val {
+                temphead = temphead.next!
+            }
+            //此时我们已经找到了合适位置，我们需要进行插入，大家可以画一画
+            last?.next = pre?.next
+            pre?.next = temphead.next
+            temphead.next = pre
+            //继续往下移动
+            pre = last?.next
+        }
+        return dummyNode.next
+    }
+}
+```