leetcode

1. 题目

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.

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

2. 关键算法

单链表的操作。

3. 代码实现

/** * @author: UniqueZ_ * @file: leetcode - Add Two Numbers    * @date: 2017-06-25 */// 节点类class ListNode {int val;ListNode next;public ListNode(int x) { val = x; }}public class AddTwoNumbers {public ListNode addTwoNumbers(ListNode l1, ListNode l2) {if (l1 == null) { return l2; }if (l2 == null) { return l1; }        ListNode tempNode = new ListNode(0);ListNode head = tempNode;int carry = 0, sum;while (l1 != null || l2 != null) {int x = (l1 == null) ? 0 : l1.val;int y = (l2 == null) ? 0 : l2.val;// 加和以及进位            sum = x + y + carry;            tempNode.val = (sum < 10) ? sum : (sum - 10);            carry = (sum < 10) ? 0 : 1;            // l1, l2向下移动if (l1 != null) { l1 = l1.next; }if (l2 != null) { l2 = l2.next; }                        // tempNode向下移动            if (l1 != null || l2 != null || carry !=0) {                tempNode.next = new ListNode(0);                tempNode = tempNode.next;            }}if (carry != 0) { tempNode.val = carry; }return head;     }// 测试程序public static void main(String[] args) {ListNode l1 = new ListNode(1);ListNode l2 = new ListNode(9);l2.next = new ListNode(9);AddTwoNumbers obj = new AddTwoNumbers();ListNode node = obj.addTwoNumbers(l1, l2);while (node != null) {System.out.println(node.val);node = node.next;}}}