Leetcode

2. Add Two Numbers

by hooni posted Apr 14, 2020
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You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.


/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode fake = new ListNode(0);
        ListNode p = fake;
        
        ListNode p1 = l1;
        ListNode p2 = l2;
        
        int carry = 0;
    
        while(p1 != null || p2 != null){
            int sum = carry;
            if(p1!=null){
                sum += p1.val;
                p1 = p1.next;
            }

            if(p2!=null){
                sum += p2.val;
                p2 = p2.next;
            }
            
            if(sum>9){
                carry=1;
                sum = sum-10;
            }else{
                carry = 0;
            }

            ListNode l = new ListNode(sum);
            p.next = l;
            p = p.next;
        }
        
        //don't forget check the carry value at the end
        if(carry > 0){
            ListNode l = new ListNode(carry);
            p.next = l;
        }
        return fake.next;
    }
}


[문제] https://leetcode.com/problems/add-two-numbers/