LeetCode-Explanations/AddTwoNumbers.cpp at main · Kurisuo/LeetCode-Explanations · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
// LeetCode (Medium) 2 : Add Two Numbers

/**
 * 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* retList = new ListNode();
        ListNode* curr = retList;
        ListNode* head = retList;
        int carry = 0;

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

            int add = (val1 + val2 + carry);
            int digit = add % 10; //extract rightmost
            carry = add / 10;     //delete rightmost

            curr -> next = new ListNode(digit);
            curr = curr -> next;

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

        return head -> next;
    }
};