LeetCode # Array # 2-Add Two Numbers

topic:

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. 

Answer : 
Since I wrote it in a hurry, I referred to the high praise answer:

/**
 * 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 prev = new ListNode(0);
        ListNode head = prev;
         int carry = 0 ;
         while (l1 != null || l2 != null || carry != 0) { // Conditional entry loop 
             ListNode cur = new ListNode(0 );
              int sum = ( (l2 == null ) ? 0 : l2.val )+ ((l1 == null ) ? 0 : l1.val) + carry; // add the current sum; 
             cur.val = sum %10; // will The one digit assignment 
             carry = sum / 10 ; // Assign the tens digit 
             prev.next = cur; // Save cur in prev. next;
             prev = cure;
             
             l1 = (l1 == null )? l1 : l1.next; // The two numbers are pushed backward. 
             l2 = (l2 == null )? l2 : l2.next;
            
        }
        return head.next;
    }
}

In the code, what needs to be understood is: the reference and assignment process of the type in java, whether the value is changing, or the index is changing.

refer to:

https://www.cnblogs.com/f-zhao/p/6380699.html

https://www.zhihu.com/question/31203609

LeetCode # Array # 2-Add Two Numbers

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