Add_Two_Numbers.cpp

//解題思路：迴圈遍歷兩個List，算出每個位數相加後紀錄carry並將該位數值放至新的Linked List
//需考慮到l1或l2誰先結束，以及是否有尚未加上的carry位
 
 //Definition for singly-linked list.
 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* sol = new ListNode(0);
        ListNode* current = sol;
        int carry = 0;

        while(l1 != nullptr || l2 != nullptr || carry != 0){
            int val1 = (l1 != nullptr) ? l1->val : 0;
            int val2 = (l2 != nullptr) ? l2 ->val : 0;

            int sum = val1 + val2 + carry;
            carry = sum / 10;
            current->next = new ListNode(sum % 10);
            current = current->next;

            if(l1 != nullptr)
                l1 = l1->next;
            if(l2 != nullptr)
                l2 = l2->next;

        }
        ListNode* result = sol->next;
        delete sol;  // Freeing the memory allocated for dummyHead
        return result;

    }
};