Leetcode: Add two numbers problem solving report

Add two numbers
You are given two linked lists representing two non-negative numbers. 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.

Input: (2-> 4-> 3) + (5-> 6-> 4)
Output: 7-> 0-> 8

Https://oj.leetcode.com/problems/add-two-numbers/

Answer:

It is relatively simple to move two pointers forward, add the values of the two lists, and calculate the carry value. Note: add carry = 1 in the while loop, so that the carry value can be automatically added to the end of the chain.

 1 package Algorithms.list; 2  3 import Algorithms.algorithm.others.ListNode; 4  5 /** 6  * Definition for singly-linked list. 7  * public class ListNode { 8  *     int val; 9  *     ListNode next;10  *     ListNode(int x) {11  *         val = x;12  *         next = null;13  *     }14  * }15  */16 public class AddTwoNumbers {17     public static void main(String[] str) {18         ListNode n1 = new ListNode(9);19         20         ListNode l1 = new ListNode(1);21         ListNode l2 = new ListNode(9);22         ListNode l3 = new ListNode(9);23         ListNode l4 = new ListNode(9);24         ListNode l5 = new ListNode(9);25         ListNode l6 = new ListNode(9);26         ListNode l7 = new ListNode(9);27         ListNode l8 = new ListNode(9);28         ListNode l9 = new ListNode(9);29         ListNode l10 = new ListNode(9);30         31         l1.next = l2;32         l2.next = l3;33         l3.next = l4;34         l4.next = l5;35         l5.next = l6;36         l6.next = l7;37         l7.next = l8;38         l8.next = l9;39         l9.next = l10;40         41         System.out.println(addTwoNumbers(n1, l1).toString());42     }43     44     public static ListNode addTwoNumbers(ListNode l1, ListNode l2) {45         if (l1 == null || l2 == null) {46             return null;47         }48         49         ListNode dummy = new ListNode(0);50         ListNode tail = dummy;51         int carry = 0;52         53         while (l1 != null || l2 != null || carry == 1) {54             int sum = carry;55             if (l1 != null) {56                 sum += l1.val;57                 l1 = l1.next;58             }59             60             if (l2 != null) {61                 sum += l2.val;62                 l2 = l2.next;63             }64             65             carry = sum / 10;66             67             // create a new node and add it to the tail.68             ListNode cur = new ListNode(sum % 10);69             tail.next = cur;70             tail = tail.next;71         }72         73         return dummy.next;74     }75 }

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Code:

Addtwonumbers

Leetcode: Add two numbers problem solving report