题目

给你两个 非空 链表来代表两个非负整数。数字最高位位于链表开始位置。它们的每个节点只存储一位数字。将这两数相加会返回一个新的链表。
你可以假设除了数字 0 之外，这两个数字都不会以零开头。
示例1：
输入：l1 = [7,2,4,3], l2 = [5,6,4]
输出：[7,8,0,7]

分析

可以先翻转链表，把最低位放到最前面然后开始进行相加，注意和超过10需要进位

public class LinkNode {int val;LinkNode next;public LinkNode(int data) {this.val = data;this.next = null;}
}
public class LinkList {LinkNode head;public LinkList() {this.head = null;}public LinkNode getHead() {return this.head;}//添加元素public void addNode(int data) {LinkNode node = new LinkNode(data);if (this.head == null) {this.head = node;} else {LinkNode cur = this.head;while(cur.next != null) {cur = cur.next;}cur.next = node;}}//正序打印public void print(LinkNode node) {while(node != null) {System.out.print(node.val);System.out.print(" ");node = node.next;}System.out.println();}public LinkNode addTwoNumbers(LinkNode l1, LinkNode l2) {LinkNode p1 = reverse(l1);LinkNode p2 = reverse(l2);int count = 0;LinkNode head = new LinkNode(-1);LinkNode p = head;while(p1 != null || p2 != null) {int numa = 0;if(p1 != null) {numa = p1.val;}int numb = 0;if(p2 != null) {numb = p2.val;}int sum = numa + numb + count;if(sum >= 10) {p.next = new LinkNode(sum % 10);count = sum / 10;} else {p.next = new LinkNode(sum);count = 0;}p = p.next;if(p1 != null) {p1 = p1.next;}if(p2 != null) {p2 = p2.next;}}if(count > 0) {p.next = new LinkNode(count);p = p.next;}LinkNode node = reverse(head.next);print(node);return node;}public LinkNode reverse(LinkNode l1) {LinkNode pre = null;while(l1 != null) {LinkNode next = l1.next;l1.next = pre;pre = l1;l1 = next;}return pre;}
}
public class addTwoNumbersII {public static void main(String[] args) {LinkList list = new LinkList();list.addNode(7);list.addNode(2);list.addNode(4);list.addNode(3);LinkList lista = new LinkList();lista.addNode(5);lista.addNode(6);lista.addNode(4);list.addTwoNumbers(list.getHead(),lista.getHead());}
}