LeetCode-2. Add Two Numbers

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

读题

题目的意思是说，给定两个非空的链表，计算两个链表所表示数的和，返回一个结果的链表，其实可以看出来就是一个大数相加的思想

题解

public class Solution2 {
public static ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode p1 = l1;
ListNode p2 = l2;
//表示进位数
int jinwei = 0;
ListNode result = new ListNode(0);

//指向结果的node
ListNode head = result;
//当前计算节点的前一个节点引用
ListNode pre = result;
int a;
int b;
while(p1!=null||p2!=null||jinwei!=0){
//如果节点的是空加数为0否则为节点的值
a = (p1 == null?0:p1.val);
b = (p2 == null?0:p2.val);
//计算进位数和本位和
result.val = (a + b +jinwei)%10;
jinwei = (a + b +jinwei)/10;
//将pre应用指向当前的计算节点
pre = result;
//创建一个新的节点result向后移动
ListNode p = new ListNode(0);
result.next = p;
result = p;
if(p1!=null)
p1 = p1.next;
if(p2!=null)
p2 = p2.next;
}
//pre最终指向最后一个节点
pre.next = null;
return head;
}

public static void print(ListNode p) {
while (p != null) {
System.out.print(p.val);
p = p.next;
if (p != null) {
System.out.print(" -> ");
}
}
}

public static void main(String[] args) {
ListNode node1 = new ListNode(1);
ListNode node2 = new ListNode(2);
ListNode node3 = new ListNode(3);
node1.next = node2;
node2.next = node3;
node3.next = null;

ListNode node4 = new ListNode(2);
ListNode node5 = new ListNode(1);
ListNode node6 = new ListNode(7);
node4.next = node5;
node5.next = node6;
node6.next = null;
//Solution2.print(node1);
Solution2.print(Solution2.addTwoNumbers(node1, node4));
}
}