Add Two Numbers

You are given twonon-emptylinked 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

Tips:

注意一下进位。

Code:

public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int carry = 0;
        int sum = 0;
        ListNode dummy = new ListNode(0);
        ListNode head = dummy;
        while (l1 != null && l2 != null) {
            sum = l1.val + l2.val + carry;
            carry = sum / 10;
            head.next = new ListNode(sum % 10);
            head = head.next;
            l1 = l1.next;
            l2 = l2.next;
        }
        while (l1 != null) {
            sum = l1.val + carry;
            carry = sum / 10;
            head.next = new ListNode(sum % 10);
            head = head.next;
            l1 = l1.next;
        }
        while (l2 != null) {
            sum = l2.val + carry;
            carry = sum / 10;
            head.next = new ListNode(sum % 10);
            head = head.next;
            l2 = l2.next;
        }
        if (carry != 0) {
            head.next = new ListNode(carry);
        }
        return dummy.next;
    }
}