2. Add Two Numbers You are given two non-empty linked 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 /** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) { * val = x; * next = null; * } * } */ //mine public class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { if(l1==null) { return l2; } if(l2==null) { return l1; } ListNode dummy = new ListNode(-1); ListNode prev = dummy; int adv = 0; while(l1!=null || l2!=null) { int sum = adv; if(l1!=null) { sum+=l1.val; l1=l1.next; } if(l2!=null) { sum+=l2.val; l2=l2.next; } adv = sum/10; prev.next = new ListNode(sum%10); prev = prev.next; } if(adv>0) { prev.next = new ListNode(adv); } return dummy.next; } } ////////////////////////////////////////////////////////////////////////////// public class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { if(l1==null) return l2; if(l2==null) return l1; int adv = 0; ListNode head = null; ListNode tail = null; while(l1!=null && l2!=null) { int sum = adv + l1.val + l2.val; int value = sum%10; adv = sum>=10 ? 1 : 0; if(head==null) { head = new ListNode(value); tail = head; } else { tail.next = new ListNode(value); tail = tail.next; } l1 = l1.next; l2 = l2.next; } ListNode p = null; if(l1!=null) { p = l1; } else if(l2!=null) { p = l2; } while(p!=null) { int sum = adv + p.val; int value = sum % 10; adv = sum>=10 ? 1 : 0; tail.next = new ListNode(value); tail = tail.next; p = p.next; } if(adv>0) tail.next = new ListNode(adv); return head; } } ////////////////////////////////////////////////////////////////////////////// public class Solution { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { if (l1 == null) return l2; if (l2 == null) return l1; ListNode head = new ListNode(0); ListNode cur = head; int plus = 0; while (l1 != null && l2 != null) { int sum = l1.val + l2.val + plus; plus = sum / 10; sum = sum % 10; cur.next = new ListNode(sum); cur = cur.next; l1 = l1.next; l2 = l2.next; } if (l1 != null) { if (plus != 0) { cur.next = addTwoNumbers(l1, new ListNode(plus)); } else { cur.next = l1; } } else if (l2 != null) { if (plus != 0) { cur.next = addTwoNumbers(l2, new ListNode(plus)); } else { cur.next = l2; } } else if (plus != 0) { cur.next = new ListNode(plus); } return head.next; } }