Leetcode. Add two numbers task
Task
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.
Example:
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.
Solution
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode() {}
* ListNode(int val) { this.val = val; }
* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
* }
*/
class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
return addTwoNumbers(l1,l2,0);
}
private ListNode addTwoNumbers(ListNode l1, ListNode l2, int delta) {
if ((l1 == null) && (l2 == null) && (delta == 0)) return null;
int val1 = (l1 == null) ? 0 : l1.val;
int val2 = (l2 == null) ? 0 : l2.val;
int val = val1 + val2 + delta;
delta = 0;
if (val > 9) {
val = val - 10;
delta = 1;
}
ListNode l3 = new ListNode(val);
ListNode nl1 = (l1 == null) ? null : l1.next;
ListNode nl2 = (l2 == null) ? null : l2.next;
l3.next = addTwoNumbers(nl1,nl2, delta);
return l3;
}
}
Results
- Runtime: 1 ms, faster than 100.00% of Java online submissions for Add Two Numbers.
- Memory Usage: 39.2 MB, less than 100.00% of Java online submissions for Add Two Numbers.