Time: 7 ms (43.78%), Space: 17.8 MB (57.75%) - LeetHub

Author: hogan-tech

0445-add-two-numbers-ii/0445-add-two-numbers-ii.py

@@ -0,0 +1,41 @@
+# time complexity: O(m+n)
+# space complexity: O(m+n)
+from typing import Optional
+
+
+
+
+
+class Solution:
+    def reverseList(self, node: Optional[ListNode]) -> Optional[ListNode]:
+        prev = None
+        while node:
+            nextNode = node.next
+            node.next = prev
+            prev = node
+            node = nextNode
+        return prev
+
+    def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:
+        r1 = self.reverseList(l1)
+        r2 = self.reverseList(l2)
+
+        totalSum = 0
+        carry = 0
+        result = ListNode()
+        while r1 or r2:
+            if r1:
+                totalSum += r1.val
+                r1 = r1.next
+            if r2:
+                totalSum += r2.val
+                r2 = r2.next
+
+            result.val = totalSum % 10
+            carry = totalSum // 10
+            head = ListNode(carry)
+            head.next = result
+            result = head
+            totalSum = carry
+
+        return result.next if carry == 0 else result