Merge pull request neetcode-gh#1232 from Mahim1997/develop/2_swift

2. Add Two Numbers

swift/2-Add-Two-Numbers.swift

@@ -0,0 +1,42 @@
+/**
+ * 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 Solution {
+ func addTwoNumbers(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+ var itr1 = l1
+ var itr2 = l2
+ var carry: Int = 0
+ var sum: Int = 0
+
+ var dummy = ListNode(0)
+ var head: ListNode? = dummy
+
+ while itr1 != nil || itr2 != nil {
+ let val1 = itr1?.val ?? 0
+ let val2 = itr2?.val ?? 0
+
+ sum = val1 + val2 + carry
+ carry = sum/10
+ sum = sum%10
+
+ head?.next = ListNode(sum)
+ head = head?.next
+
+ itr1 = itr1?.next
+ itr2 = itr2?.next 
+ }
+
+ if carry > 0 {
+ head?.next = ListNode(carry)
+ }
+
+ return dummy.next
+ }
+}