/*AddTwoNumbers.java

Add Two Numbers

You have two numbers represented by a linked list, where each node contains a single digit. The digits are stored in reverse order, such that the 1's digit is at the head of the list. Write a function that adds the two numbers and returns the sum as a linked list.

Example

Given 7->1->6 + 5->9->2. That is, 617 + 295.

Return 2->1->9. That is 912.

Given 3->1->5 and 5->9->2, return 8->0->8.

Tags Cracking The Coding Interview Linked List High Precision

*/

public class AddTwoNumbers {

/**

* @param l1: the first list

* @param l2: the second list

* @return: the sum list of l1 and l2

*/

public ListNode addLists(ListNode l1, ListNode l2) {

// write your code here

int digit = 0;

ListNode dummy = new ListNode(0);

ListNode head = dummy;

while (l1 != null && l2 != null) {

int val = l1.val + l2.val + digit;

digit = val / 10;

ListNode node = new ListNode(val % 10);

node.next = head.next;

head.next = node;

l1 = l1.next;

l2 = l2.next;

head = head.next;

}

//Missing Condition before AC

if (l1 == null & l2 == null && digit > 0) {

ListNode digitNode = new ListNode(digit);

head.next = digitNode;

}

if (l1 != null) {

head.next = l1;

while (digit > 0) {

l1.val = (l1.val + digit) % 10;

digit = (l1.val + digit) / 10;

l1 = l1.next;

}

}

if (l2 != null) {

head.next = l2;

while (digit > 0) {

l2.val = (l2.val + digit) % 10;

digit = (l2.val + digit) / 10;

l2 = l2.next;

}

}

return dummy.next;

}

}