p2

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LeetCode p2 Add Two Numbers 题解

1.题目：

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

题意：

输入两个链表，输出他们的和。（有进位，见示例）

2.解题思路:

见代码

3.代码

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode ansListNode = null;
		ListNode head = null;
		int flag = 0;
		while (l1 != null || l2 != null) {
			int a = 0;
			if (l1 != null)
				a += l1.val;
			if (l2 != null)
				a += l2.val;
			a += flag;
			if (ansListNode == null) {
				ansListNode = new ListNode(a % 10);
				head = ansListNode;
				flag = a / 10;
				if (l1 != null)
					l1 = l1.next;
				if (l2 != null)
					l2 = l2.next;
				continue;
			}

			else {
				ansListNode.next = new ListNode(a % 10);
			}
			flag = a / 10;
			ansListNode = ansListNode.next;
			
			if (l1 != null)
				l1 = l1.next;
			if (l2 != null)
				l2 = l2.next;
		}

		while (flag > 0) {
			ansListNode.next = new ListNode(flag % 10);
			ansListNode = ansListNode.next;
			flag = flag / 10;
		}
		return head;
    }
}

4.一些总结：