链表求和
题目
你有两个用链表代表的整数,其中每个节点包含一个数字。数字存储按照在原来整数中相反的顺序,使得第一个数字位于链表的开头。写出一个函数将两个整数相加,用链表形式返回和。
样例
给出两个链表 3->1->5->null 和 5->9->2->null,返回 8->0->8->null
题解
主要难点在于处理进位问题。
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
/**
* @param l1: the first list
* @param l2: the second list
* @return: the sum list of l1 and l2
*/
public ListNode addLists(ListNode l1, ListNode l2) {
if(l1 == null && l2 == null)
{
return null;
}
ListNode head = new ListNode(0);
ListNode point = head;
int carry = 0;
while(l1 != null && l2!=null)
{
int sum = carry + l1.val + l2.val;
point.next = new ListNode(sum % 10);
carry = sum / 10;
l1 = l1.next;
l2 = l2.next;
point = point.next;
}
while(l1 != null)
{
int sum = carry + l1.val;
point.next = new ListNode(sum % 10);
carry = sum /10;
l1 = l1.next;
point = point.next;
}
while(l2 != null)
{
int sum = carry + l2.val;
point.next = new ListNode(sum % 10);
carry = sum /10;
l2 = l2.next;
point = point.next;
}
if (carry != 0)
{
point.next = new ListNode(carry);
}
return head.next;
}
}
Last Update 2016.9.7