leetcode刷题详解——Add Two Numbers(02)

题目地址:https://leetcode.com/problems/add-two-numbers/#/description


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

题目解析:

这道题主要是考察列表和数字相加,意思简单,但是需要注意一下两点:

1.如何处理不同长度的数字,即两个列表长度不一样

2.以及进位和最高位的判断


方法解析:

1.递归的方法

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
	public static ListNode addTwoNumbers(ListNode l1, ListNode l2) {
		return process(l1,l2,0);
    }
	public static ListNode process(ListNode l1,ListNode l2,int jinwei){
		if(l1==null && l2 == null){
			return jinwei==0?null : new ListNode(jinwei);
		}
		if(l1==null && l2!=null){
			//如果l1为空补0
			l1 = new ListNode(0);
		}
		if(l2==null && l1!=null){
			//入伙l2为空补0
			l2 = new ListNode(0);
		}
		int sum  = l1.val + l2.val + jinwei;
		ListNode node = new ListNode(sum%10);
		node.next = process(l1.next,l2.next,sum/10);
		return node;
		
	}


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