feat: add swift implementation to lcci problem: No.02.02 (doocs#2615)

Signed-off-by: Lanre Adedara

Author: klever34

lcci/02.02.Kth Node From End of List/README.md

@@ -203,6 +203,40 @@ var kthToLast = function (head, k) {
 };
 ```
 
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     var val: Int
+ *     var next: ListNode?
+ *     init(_ x: Int, _ next: ListNode? = nil) {
+ *         self.val = x
+ *         self.next = next
+ *     }
+ * }
+ */
+
+class Solution {
+    func kthToLast(_ head: ListNode?, _ k: Int) -> Int {
+        var slow = head
+        var fast = head
+        var k = k
+
+        while k > 0 {
+            fast = fast?.next
+            k -= 1
+        }
+
+        while fast != nil {
+            slow = slow?.next
+            fast = fast?.next
+        }
+
+        return slow?.val ?? 0
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/02.02.Kth Node From End of List/README_EN.md

@@ -205,6 +205,40 @@ var kthToLast = function (head, k) {
 };
 ```
 
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     var val: Int
+ *     var next: ListNode?
+ *     init(_ x: Int, _ next: ListNode? = nil) {
+ *         self.val = x
+ *         self.next = next
+ *     }
+ * }
+ */
+
+class Solution {
+    func kthToLast(_ head: ListNode?, _ k: Int) -> Int {
+        var slow = head
+        var fast = head
+        var k = k
+
+        while k > 0 {
+            fast = fast?.next
+            k -= 1
+        }
+
+        while fast != nil {
+            slow = slow?.next
+            fast = fast?.next
+        }
+
+        return slow?.val ?? 0
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- end -->

lcci/02.02.Kth Node From End of List/Solution.swift

@@ -0,0 +1,31 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     var val: Int
+ *     var next: ListNode?
+ *     init(_ x: Int, _ next: ListNode? = nil) {
+ *         self.val = x
+ *         self.next = next
+ *     }
+ * }
+ */
+
+class Solution {
+    func kthToLast(_ head: ListNode?, _ k: Int) -> Int {
+        var slow = head
+        var fast = head
+        var k = k
+        
+        while k > 0 {
+            fast = fast?.next
+            k -= 1
+        }
+        
+        while fast != nil {
+            slow = slow?.next
+            fast = fast?.next
+        }
+        
+        return slow?.val ?? 0
+    }
+}