Add Two Numbers

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { *         val = x; *         next = null; *     } * } */public class Solution {    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {        ListNode dummy = new ListNode(0);        ListNode itr = dummy;        ListNode p1 = l1, p2 = l2;        boolean hasCarry = false;        while(p1 != null || p2 != null) {            int a1 = p1 == null ? 0 : p1.val;            int a2 = p2 == null ? 0 : p2.val;            int a = hasCarry ? a1 + a2 + 1 : a1 + a2;            hasCarry = a >= 10 ? true : false;            a %= 10;            itr.next = new ListNode(a);            p1 = p1 == null ? null : p1.next;            p2 = p2 == null ? null : p2.next;            itr = itr.next;        }        itr.next = hasCarry ? new ListNode(1) : null;        return dummy.next;    }}

Time: O(n)

Space: O(1)