Added accepted solutions for leetcode number 1 and 2 problems

2-add-two-numbers.cpp

@@ -0,0 +1,43 @@
+
+struct ListNode {
+      int val;
+      ListNode *next;
+      ListNode() : val(0), next(nullptr) {}
+      ListNode(int x) : val(x), next(nullptr) {}
+      ListNode(int x, ListNode *next) : val(x), next(next) {}
+  };
+
+class AddTwoNumbersSolution {
+public:
+    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
+        
+        if (!l1 && !l2) return nullptr;
+
+        ListNode* res = new ListNode(0);
+        ListNode* start = res;
+        ListNode* prev(nullptr);
+
+        int carry = 0;
+        while (l1 || l2) {
+            res->val += (l1? l1->val : 0);
+            res->val += (l2? l2->val : 0);
+            res->val += carry;
+            carry = res->val / 10;
+            if (carry) res->val -= 10;
+            
+            res->next = new ListNode(0);
+            prev = res;
+            res = res->next;
+            if (l1) l1 = l1->next;
+            if (l2) l2 = l2->next;
+        }
+        if ((carry == 0) && prev) {
+            delete prev->next;
+            prev->next = nullptr;
+        }
+        if (carry > 0) {
+            res->val++;
+        }
+        return start;
+    }
+};