LeetCode-in-All
2. Add Two Numbers
Medium
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 contains a single digit. Add the two numbers and return the sum as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
Example 1:
Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.
Example 2:
Input: l1 = [0], l2 = [0]
Output: [0]
Example 3:
Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
Output: [8,9,9,9,0,0,0,1]
Constraints:
- The number of nodes in each linked list is in the range
[1, 100]. 0 <= Node.val <= 9- It is guaranteed that the list represents a number that does not have leading zeros.
Solution
import com_github_leetcode.ListNode
/*
* Definition for singly-linked list.
* class ListNode(_x: Int = 0, _next: ListNode = null) {
* var next: ListNode = _next
* var x: Int = _x
* }
*/
object Solution {
def addTwoNumbers(l1: ListNode, l2: ListNode): ListNode = {
val dummyHead = new ListNode(0)
var p = l1
var q = l2
var curr = dummyHead
var carry = 0
while (p != null || q != null) {
val x = if (p != null) p.x else 0
val y = if (q != null) q.x else 0
val sum = carry + x + y
carry = sum / 10
curr.next = new ListNode(sum % 10)
curr = curr.next
if (p != null) p = p.next
if (q != null) q = q.next
}
if (carry > 0) {
curr.next = new ListNode(carry)
}
dummyHead.next
}
}