feat: add swift implementation to lcof2 problem: No.025

Author: klever34

lcof2/剑指 Offer II 025. 链表中的两数相加/README.md

@@ -209,6 +209,54 @@ func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
 }
 ```
 
+#### Swift
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     var val: Int
+ *     var next: ListNode?
+ *     init() { self.val = 0; self.next = nil; }
+ *     init(_ val: Int) { self.val = val; self.next = nil; }
+ *     init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+ 
+class Solution {
+    func addTwoNumbers(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+        var s1: [Int] = []
+        var s2: [Int] = []
+        
+        var node1 = l1
+        var node2 = l2
+        
+        while let n1 = node1 {
+            s1.append(n1.val)
+            node1 = n1.next
+        }
+        
+        while let n2 = node2 {
+            s2.append(n2.val)
+            node2 = n2.next
+        }
+        
+        var carry = 0
+        let dummy: ListNode? = ListNode(0)
+        
+        while !s1.isEmpty || !s2.isEmpty || carry != 0 {
+            carry += (s1.isEmpty ? 0 : s1.removeLast()) + (s2.isEmpty ? 0 : s2.removeLast())
+            let node = ListNode(carry % 10)
+            node.next = dummy?.next
+            dummy?.next = node
+            carry /= 10
+        }
+        
+        return dummy?.next
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 025. 链表中的两数相加/Solution.swift

@@ -0,0 +1,43 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     var val: Int
+ *     var next: ListNode?
+ *     init() { self.val = 0; self.next = nil; }
+ *     init(_ val: Int) { self.val = val; self.next = nil; }
+ *     init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+ 
+class Solution {
+    func addTwoNumbers(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+        var s1: [Int] = []
+        var s2: [Int] = []
+        
+        var node1 = l1
+        var node2 = l2
+        
+        while let n1 = node1 {
+            s1.append(n1.val)
+            node1 = n1.next
+        }
+        
+        while let n2 = node2 {
+            s2.append(n2.val)
+            node2 = n2.next
+        }
+        
+        var carry = 0
+        let dummy: ListNode? = ListNode(0)
+        
+        while !s1.isEmpty || !s2.isEmpty || carry != 0 {
+            carry += (s1.isEmpty ? 0 : s1.removeLast()) + (s2.isEmpty ? 0 : s2.removeLast())
+            let node = ListNode(carry % 10)
+            node.next = dummy?.next
+            dummy?.next = node
+            carry /= 10
+        }
+        
+        return dummy?.next
+    }
+}