Add description to question2

Author: KongJHong

solution/002.Add Two Numbers/README.md

@@ -98,4 +98,45 @@ class Solution {
         return res.next;
     }
 }
-```
+```
+#### CPP
+```CPP
+class Solution {
+public:
+    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
+
+        ListNode *ans_l = new ListNode(0);
+        ListNode *head = ans_l;
+        int tmp = 0;
+        while(l1 != NULL && l2 != NULL){
+            tmp += l1->val + l2->val;
+            ans_l->next = new ListNode(tmp % 10);
+            tmp = tmp / 10;
+            ans_l = ans_l->next;
+            l1 = l1->next;
+            l2 = l2->next;
+        }
+        
+        while(l1 != NULL){
+            tmp += l1->val;
+            ans_l->next = new ListNode(tmp % 10);
+            tmp = tmp / 10;
+            ans_l = ans_l->next;
+            l1 = l1->next;  
+        }
+        
+        while(l2 != NULL){
+            tmp += l2->val;
+            ans_l->next = new ListNode(tmp % 10);
+            tmp = tmp / 10;
+            ans_l = ans_l->next;
+            l2 = l2->next;  
+        }
+        
+        if(tmp)ans_l->next = new ListNode(tmp);
+
+        return head->next;
+    }
+};
+
+```