[LeetCode] Add Two Numbers

1. 문제 : https://leetcode.com/problems/add-two-numbers/description/

 

2. 풀이

ListNode를 만들어주는 방법도 있다!

 

3. 코드

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode node = new ListNode(0);
        ListNode result = node;
        int carry = 0;
        
        while (l1 != null || l2 != null) {
            int sum = carry;
            
            if (l1 != null) {
                sum += l1.val;
                l1 = l1.next;
            }
            
            if (l2 != null) {
                sum += l2.val;
                l2 = l2.next;
            }
            
            if (sum >= 10) {
                node.next = new ListNode(sum - 10);
                carry = 1;
            } else {
                node.next = new ListNode(sum);
                carry = 0;
            }
            
            node = node.next;
        }
        
        if (carry == 1) {
            node.next = new ListNode(1);
        }
        
        return result.next;
    }
}