Create MergeTwoSortedLists.php

Author: ivanDevPHP

Easy/MergeTwoSortedLists.php

@@ -0,0 +1,54 @@
+
+<?php
+
+/**
+ * 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 $list1
+     * @param ListNode $list2
+     * @return ListNode
+     */
+    function mergeTwoLists($list1, $list2) {
+        $dummy = new ListNode();
+        $current = $dummy;
+
+        if ($list1 === null) return $list2;
+        if ($list2 === null) return $list1;
+
+        $this->merge($list1, $list2, $current);
+        
+        return $dummy->next;
+    }
+
+    function merge($head1, $head2, &$mergedList) {
+        if ($head1 === null) {
+            $mergedList->next = $head2;
+            return;
+        }
+        if ($head2 === null) {
+            $mergedList->next = $head1;
+            return;
+        }
+
+        if ($head1->val <= $head2->val) {
+            $mergedList->next = $head1;
+            $mergedList = $mergedList->next;
+            $this->merge($head1->next, $head2, $mergedList);
+        } else {
+            $mergedList->next = $head2;
+            $mergedList = $mergedList->next;
+            $this->merge($head1, $head2->next, $mergedList);
+        }
+    }
+}