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LeetCode: Add Two Numbers 解题报告
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/
解答：
比较简单，直接用2个指针往后移动，并且将2个list的值相加，并且计算上carry值。注意，在while循环中加上carry == 1的判断，这样可以自动在链尾加上carry 的值。
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 }
代码：
AddTwoNumbers
LeetCode: Add Two Numbers 解题报告
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