Added task 2

Author: javadev

composer.json

@@ -26,7 +26,7 @@
   },
   "autoload-dev": {
     "psr-4": {
-      "leetcode\\tests\\": "src/test/php/"
+      "leetcode\\": "src/test/php/"
     }
   },
   "extra": {

src/main/php/com_github_leetcode/ListNode.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace leetcode\com_github_leetcode;
+
+class ListNode {
+    public $val;
+    public $next;
+
+    public function __construct($val = 0, $next = null) {
+        $this->val = $val;
+        $this->next = $next;
+    }
+
+    public function toString() {
+        $result = (string) $this->val;
+
+        if ($this->next !== null) {
+            $current = $this->next;
+
+            while ($current->next !== null) {
+                $result .= ', ' . $current->val;
+                $current = $current->next;
+            }
+
+            $result .= ', ' . $current->val;
+        }
+
+        return $result;
+    }
+}

src/main/php/g0001_0100/s0002_add_two_numbers/Solution.php

@@ -0,0 +1,58 @@
+<?php
+
+namespace leetcode\g0001_0100\s0002_add_two_numbers;
+
+// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Math #Linked_List #Recursion
+// #Data_Structure_II_Day_10_Linked_List #Programming_Skills_II_Day_15
+// #Big_O_Time_O(max(N,M))_Space_O(max(N,M)) #2023_11_29_Time_13_ms_(73.83%)_Space_19.2_MB_(38.29%)
+
+use leetcode\com_github_leetcode\ListNode;
+
+/**
+ * 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) {
+        $dummyHead = new ListNode(0);
+        $p = $l1;
+        $q = $l2;
+        $curr = $dummyHead;
+        $carry = 0;
+        
+        while ($p !== null || $q !== null) {
+            $x = ($p !== null) ? $p->val : 0;
+            $y = ($q !== null) ? $q->val : 0;
+            $sum = $carry + $x + $y;
+            $carry = (int)($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);
+        }
+        
+        return $dummyHead->next;
+    }
+}

src/main/php/g0001_0100/s0002_add_two_numbers/readme.md

@@ -0,0 +1,35 @@
+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:**
+
+![](https://assets.leetcode.com/uploads/2020/10/02/addtwonumber1.jpg)
+
+**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.

src/test/php/com_github_leetcode/LinkedListUtils.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace leetcode\com_github_leetcode;
+
+use leetcode\com_github_leetcode\ListNode;
+
+class LinkedListUtils {
+    public static function constructLinkedList($nums) {
+        if ($nums === null || count($nums) === 0) {
+            return null;
+        }
+        $pre = new ListNode(-1);
+        $head = new ListNode($nums[0]);
+        $pre->next = $head;
+        for ($i = 1; $i < count($nums); $i++) {
+            $head->next = new ListNode($nums[$i]);
+            $head = $head->next;
+        }
+        return $pre->next;
+    }
+
+    public static function createSinglyLinkedList($listValues) {
+        if ($listValues === null || count($listValues) === 0) {
+            throw new InvalidArgumentException(
+                "Please pass in a valid listValues to create a singly linked list."
+            );
+        }
+        $head = new ListNode($listValues[0]);
+        $tmp = $head;
+        for ($i = 1; $i < count($listValues); $i++) {
+            $next = new ListNode($listValues[$i]);
+            $tmp->next = $next;
+            $tmp = $tmp->next;
+        }
+        return $head;
+    }
+}

src/test/php/g0001_0100/s0002_add_two_numbers/SolutionTest.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace leetcode\g0001_0100\s0002_add_two_numbers;
+
+use PHPUnit\Framework\TestCase;
+use leetcode\com_github_leetcode\ListNode;
+use leetcode\com_github_leetcode\LinkedListUtils;
+
+class SolutionTest extends TestCase {
+    public function testAddTwoNumbers() {
+        $listNode1 = LinkedListUtils::constructLinkedList([2, 4, 3]);
+        $listNode2 = LinkedListUtils::constructLinkedList([5, 6, 4]);
+        $this->assertThat(
+            (new Solution())->addTwoNumbers($listNode1, $listNode2)->toString(),
+            $this->equalTo("7, 0, 8")
+        );
+    }
+
+    public function testAddTwoNumbers2() {
+        $this->assertThat(
+            (new Solution())->addTwoNumbers(new ListNode(0), new ListNode(0))->toString(),
+            $this->equalTo("0")
+        );
+    }
+
+    public function testAddTwoNumbers3() {
+        $listNode1 = LinkedListUtils::constructLinkedList([9, 9, 9, 9, 9, 9, 9]);
+        $listNode2 = LinkedListUtils::constructLinkedList([9, 9, 9, 9]);
+        $this->assertThat(
+            (new Solution())->addTwoNumbers($listNode1, $listNode2)->toString(),
+            $this->equalTo("8, 9, 9, 9, 0, 0, 0, 1")
+        );
+    }
+}