feat: 2_add_two_numbers

2_add_two_numbers/main.cpp

@@ -0,0 +1,53 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+
+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 Solution {
+public:
+    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
+        ListNode* result = new ListNode{0, nullptr};
+        ListNode* lastNode = nullptr;
+        ListNode* currentNode = result;
+        int carry = 0;
+
+        while (l1 != nullptr || l2 != nullptr) {
+            int n1 = 0, n2 = 0;
+
+            if (l1 != nullptr) {
+                n1 = l1->val;
+                l1 = l1->next;
+            }
+
+            if (l2 != nullptr) {
+                n2 = l2->val;
+                l2 = l2->next;
+            }
+
+            int s = n1 + n2 + carry;
+            carry = s / 10;
+            s = s % 10;
+
+            currentNode->val = s;
+            currentNode->next = new ListNode{0, nullptr};
+            lastNode = currentNode;
+            currentNode = currentNode->next;
+        }
+
+        if (carry > 0) {
+            currentNode->val = carry;
+        } else if (lastNode != nullptr) {
+            delete lastNode->next;
+            lastNode->next = nullptr;
+        }
+
+        return result;
+    }
+};