package org.redquark.tutorials.leetcode;
/**
* @author Anirudh
*/
public class AddTwoNumbers {
private static ListNode addTwoNumbers(ListNode l1, ListNode l2) {
// Head of the new linked list - this is the head of the resultant list
ListNode head = null;
// Reference of head which is null at this point
ListNode temp = null;
// Carry
int carry = 0;
// Loop for the two lists
while (l1 != null || l2 != null) {
// At the start of each iteration, we should add carry from the last iteration
int sum = carry;
// Since the lengths of the lists may be unequal, we are checking if the
// current node is null for one of the lists
if (l1 != null) {
sum += l1.val;
l1 = l1.next;
}
if (l2 != null) {
sum += l2.val;
l2 = l2.next;
}
// At this point, we will add the total sum % 10 to the new node
// in the resultant list
ListNode node = new ListNode(sum % 10);
// Carry to be added in the next iteration
carry = sum / 10;
// If this is the first node or head
if (temp == null) {
temp = head = node;
}
// For any other node
else {
temp.next = node;
temp = temp.next;
}
}
// After the last iteration, we will check if there is carry left
// If it's left then we will create a new node and add it
if (carry > 0) {
temp.next = new ListNode(carry);
}
return head;
}
}