Add Two Numbers

src/s2_add_two_numbers.cpp

@@ -0,0 +1,23 @@
+#include "s2_add_two_numbers.hpp"
+
+ListNode* Solution::addTwoNumbers(ListNode* l1, ListNode* l2) {
+  ListNode *l_begin = new ListNode((l1->val + l2->val) % 10);
+  ListNode *l_end = l_begin;
+  int carry{ (l1->val + l2->val) >= 10 ? 1 : 0 };
+  while (l1->next != nullptr || l2->next != nullptr || carry != 0) {
+    if (l1->next == nullptr && l2->next != nullptr) {
+      l1->next = new ListNode(0);
+    } else if (l1->next != nullptr && l2->next == nullptr) {
+      l2->next = new ListNode(0);
+    } else if (l1->next == nullptr && l2->next == nullptr && carry != 0) {
+      l1->next = new ListNode(0);
+      l2->next = new ListNode(0);
+    }
+    l1 = l1->next;
+    l2 = l2->next;
+    l_end->next = new ListNode((l1->val + l2->val + carry) % 10);
+    l_end = l_end->next;
+    carry = (l1->val + l2->val + carry) >= 10 ? 1 : 0;
+  }
+  return l_begin;
+}