LeetCode | Add Two Numbers

题目

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

分析

按照题目要求求和，注意最高位是否是进位得到的1.

代码

public class AddTwoNumbers {
	public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
		ListNode dummy = new ListNode(0);
		ListNode p = dummy;
		int carry = 0;
		while (l1 != null && l2 != null) {
			int sum = carry + l1.val + l2.val;
			carry = 0;
			if (sum >= 10) {
				carry = 1;
				sum -= 10;
			}
			p.next = new ListNode(sum);
			p = p.next;
			l1 = l1.next;
			l2 = l2.next;
		}
		if (l1 == null) {
			l1 = l2;
		}
		while (l1 != null) {
			int sum = carry + l1.val;
			carry = 0;
			if (sum >= 10) {
				carry = 1;
				sum -= 10;
			}
			p.next = new ListNode(sum);
			p = p.next;
			l1 = l1.next;
		}
		p.next = carry == 1 ? new ListNode(1) : null;
		return dummy.next;
	}
}