【LeetCode】Add Two Numbers

题目描述

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

问题分析

这是一个简单的数字相加，主要边界条件和进位就行

代码

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode res = new ListNode(0);
        ListNode head=res;
        int flag=0;
        int carry=0;
        while (l1!=null || l2!=null)
        {
            int s=0;
            if(l1!=null)
            {
                s=l1.val;
                l1=l1.next;
            }
            if(l2!=null)
            {
                s+=l2.val;
                l2=l2.next;
            }
            s+=carry;
            if(flag==0)
            {
                res.val=s%10;
                flag=1;
            }
            else
            {
                res.next=new ListNode(s%10);
                res=res.next;
            }
            if(s>=10)
            {
                carry=1;
            }
            else
            {
                carry=0;
            }
        }
        if(carry==1)
        {
            res.next=new ListNode(1);
        }
        return head;     
    }
}

总结

这个问题并不是很难，注意一些边界条件还是很容易的

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