445. Add Two Numbers II
Medium
You are given two non-empty linked lists representing two non-negative integers. The most significant digit comes first 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 = [7,2,4,3], l2 = [5,6,4]
Output: [7,8,0,7]
Example 2:
Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [8,0,7]
Example 3:
Input: l1 = [0], l2 = [0]
Output: [0]
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.
Follow-up: Could you solve it without reversing the input lists?
Solution:
* Definition for a singly-linked list.
* class ListNode {
* public $val = 0;
* public $next = null;
* function __construct($val = 0, $next = null) {
* $this->val = $val;
* $this->next = $next;
* }
* }
*/
class Solution {
/**
* @param ListNode $l1
* @param ListNode $l2
* @return ListNode
*/
function addTwoNumbers($l1, $l2) {
$s1 = new SplStack();
$s2 = new SplStack();
while($l1 != null){
$s1->push($l1->val);
$l1 = $l1->next;
}
while($l2 != null){
$s2->push($l2->val);
$l2 = $l2->next;
}
$sum = 0;
$cur = new ListNode();
while(!$s1->isEmpty() || !$s2->isEmpty()){
if(!$s1->isEmpty()) $sum += $s1->pop();
if(!$s2->isEmpty()) $sum += $s2->pop();
$cur->val = $sum%10;
$head = new ListNode(floor($sum/10));
$head->next = $cur; // reconstruct
$cur = $head;// moving on
$sum /= 10;
}
if($cur->val >= 1 ){
$return_value = 0? $cur->next: $cur;
}else{
$return_value = $cur->next;
}
return ($return_value);
//return $cur->val == 0? $cur->next: $cur;
}
}
