Leetcode

Leetcode - Add Two Numbers

问题描述

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.

Example

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

算法实现

按照加法运算法则生成新节点，注意5+5=10即和比加数要长时，处理进位的情况

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int val1,val2,carry=0;
        ListNode head=new ListNode(0);
        ListNode curr=head;
        while(l1!=null || l2!=null){
            val1=0;val2=0;
            if(l1!=null) val1=l1.val;
            if(l2!=null) val2=l2.val;
            
            int sum=carry+val1+val2;
            carry=sum/10;
            curr.next=new ListNode(sum%10);
            curr=curr.next;
            
            if(l1!=null) l1=l1.next;
            if(l2!=null) l2=l2.next;
        }
        if(carry>0) curr.next=new ListNode(carry);
        return head.next;
    }
}