Create 0143-reorder-list.swift

Author: drxlx

swift/0143-reorder-list.swift

@@ -0,0 +1,48 @@
+/**
+ * Question Link: https://leetcode.com/problems/reorder-list/
+ */
+
+ /**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class ReorderList {
+    func reorderList(_ head: ListNode?) {
+        var slow = head
+        var fast = head?.next
+
+        while fast != nil || fast?.next != nil {
+            slow = slow?.next
+            fast = fast?.next?.next
+        }
+
+        var second = slow?.next
+        slow?.next = nil
+        var prev: ListNode?
+
+        while second != nil {
+            var temp = second?.next
+            second?.next = prev
+            prev = second
+            second = temp
+        }
+
+        var first = head
+        second = prev
+
+        while second != nil {
+            var temp1 = first?.next
+            var temp2 = second?.next
+            first?.next = second
+            second?.next = temp1
+            first = temp1
+            second = temp2
+        }
+    }
+}