leetcode Add Two Numbers 难度系数3 3.1

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本文介绍了如何通过链表结构来实现两个非负整数的相加运算，包括代码实现和详细步骤解释。

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Question：

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

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
   public static ListNode addTwoNumbers(ListNode l1, ListNode l2) {

		ListNode p1 = l1;
		ListNode p2 = l2;
		ListNode result = null;
		ListNode temp = result;
		int carry = 0;

		while (p1 != null && p2 != null) {
			int number = p1.val + p2.val + carry;
			if (number < 10) {
				carry = 0;
			} else {
				number -= 10;
				carry = 1;
			}
			ListNode node = new ListNode(number);
			if (result == null) {
				result = node;
			} else {
				temp.next = node;
			}
			temp = node;
			p1 = p1.next;
			p2 = p2.next;
		}

		while (p1 != null) {
			int number = p1.val + carry;
			if (number < 10) {
				carry = 0;
			} else {
				number -= 10;
				carry = 1;
			}
			ListNode node = new ListNode(number);
			temp.next = node;
			temp = node;
			p1 = p1.next;
		}

		while (p2 != null) {
			int number = p2.val + carry;
			if (number < 10) {
				carry = 0;
			} else {
				number -= 10;
				carry = 1;
			}
			ListNode node = new ListNode(number);
			temp.next = node;
			temp = node;
			p2 = p2.next;
		}

		if (p1 == null && p2 == null && carry != 0) {
			ListNode node = new ListNode(carry);
			temp.next = node;
		}
		return result;
	}
}