feat: fix for CI warnings in 2.cpp

Author: nageshnnazare

leetcode/src/2.cpp

@@ -3,36 +3,38 @@
  * Add the two numbersand return the sum as a linked list.
  */
 
-/*
+#include <memory>
+
+ /*
  * Definition for singly-linked list.
  */
 struct ListNode {
     int val;
     ListNode *next;
-    ListNode() : val(0), next(nullptr) {}
+    explicit ListNode() : val(0), next(nullptr) {}
     ListNode(int x) : val(x), next(nullptr) {}
     ListNode(int x, ListNode *next) : val(x), next(next) {}
 };
 
 class Solution {
 public:
-    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
-        int carry = 0;
-        ListNode head;
-        ListNode* sum = &head;
-
-        while (l1 || l2) {
-            int val = carry + (l1 ? l1->val : 0) + (l2 ? l2->val : 0);
-            carry = val / 10;
-            sum->next = new ListNode(val % 10);
-            sum = sum->next;
-            l1 = (l1 ? l1->next : nullptr);
-            l2 = (l2 ? l2->next : nullptr);
-        }
-        if (carry) {
-            sum->next = new ListNode(carry);
-        }
+ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
+    int carry = 0;
+    std::unique_ptr<ListNode> head(new ListNode(0));
+    ListNode* sum = head.get();
 
-        return head.next;
+    while(l1 || l2) {
+        int val = carry + (l1 ? l1->val : 0) + (l2 ? l2->val : 0);
+        carry = val/10;
+        sum->next = new ListNode(val%10);
+        sum = sum->next;
+        l1 = (l1 ? l1->next : nullptr);
+        l2 = (l2 ? l2->next : nullptr);
     }
+    if(carry){
+        sum->next = new ListNode(carry);
+    }
+
+    return head->next;
+}
 };