A fominichev/hw6

.gitignore

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+/nbproject/

README.md

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-# PHP_2022
+PHP Developer. Professional
+
+# Решить задачу Leetcode
+
+Слияние двух списков
+
+https://leetcode.com/problems/merge-two-sorted-lists/
+
+Каждый список пройден один раз. Общее количество итераций циклов равно сумме количества элементов обоих списков. Следовательно, сложность алгоритма - O(n).

leetcode.php

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+/**
+ * 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 {
+
+    private $_result_head = null;
+    private $_result_tail = null;
+
+    /**
+     * @param ListNode $list1
+     * @param ListNode $list2
+     * @return ListNode
+     */
+    function mergeTwoLists($list1, $list2) {
+        while ($list1 !== null) {
+            while ($list2 !== null && $list2->val < $list1->val) {
+                $list2 = $this->_solution_step($list2);
+            }
+            $list1 = $this->_solution_step($list1);
+        }
+        while ($list2 !== null) {
+            $list2 = $this->_solution_step($list2);
+        }
+        return $this->_result_head;
+    }
+
+    /**
+     * @param ListNode $add_node
+     * @return ListNode
+     */
+    private function _solution_step(ListNode $add_node): ?ListNode {
+        $this->_update_solution(new ListNode($add_node->val));
+        $new_tail = $add_node->next;
+        return $new_tail;
+    }
+
+    /**
+     * @param ListNode $add_node
+     * @return void
+     */
+    private function _update_solution(ListNode $add_node): void {
+        $this->_result_tail = self::add_node_to_list_tail($this->_result_tail, $add_node);
+        $this->_result_head = self::set_list_head($this->_result_head, $add_node);
+    }
+
+    /**
+     * @param ListNode $list_tail
+     * @param ListNode $add_node
+     * @return ListNode
+     */
+    private static function add_node_to_list_tail(?ListNode $list_tail, ListNode $add_node): ListNode {
+        if ($list_tail !== null) {
+            $list_tail->next = $add_node;
+        }
+        return $add_node;
+    }
+
+    /**
+     * @param ListNode $list_head
+     * @param ListNode $list_tail
+     * @return ListNode
+     */
+    private static function set_list_head(?ListNode $list_head, ListNode $list_tail): ListNode {
+        if ($list_head === null) {
+            $list_head = $list_tail;
+        }
+        return $list_head;
+    }
+
+}

leetcode_improved.php

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+/**
+ * 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 {
+
+    private $_result_head = null;
+    private $_result_tail = null;
+
+    /**
+     * @param ListNode $list1
+     * @param ListNode $list2
+     * @return ListNode
+     */
+    function mergeTwoLists($list1, $list2) {
+        while ($list1 !== null && $list2 !== null) {
+            if ($list2->val < $list1->val) {
+                $list2 = $this->_solution_step($list2);
+            } else {
+                $list1 = $this->_solution_step($list1);
+            }
+        }
+        if ($list1 !== null) {
+            $list1 = $this->_update_solution($list1);
+        } elseif ($list2 !== null) {
+            $list2 = $this->_update_solution($list2);
+        }
+        return $this->_result_head;
+    }    
+
+    /**
+     * @param ListNode $add_node
+     * @return ListNode
+     */
+    private function _solution_step(ListNode $add_node): ?ListNode {
+        $this->_update_solution(new ListNode($add_node->val));
+        $new_tail = $add_node->next;
+        return $new_tail;
+    }
+
+    /**
+     * @param ListNode $add_node
+     * @return void
+     */
+    private function _update_solution(ListNode $add_node): void {
+        $this->_result_tail = self::add_node_to_list_tail($this->_result_tail, $add_node);
+        $this->_result_head = self::set_list_head($this->_result_head, $add_node);
+    }
+
+    /**
+     * @param ListNode $list_tail
+     * @param ListNode $add_node
+     * @return ListNode
+     */
+    private static function add_node_to_list_tail(?ListNode $list_tail, ListNode $add_node): ListNode {
+        if ($list_tail !== null) {
+            $list_tail->next = $add_node;
+        }
+        return $add_node;
+    }
+
+    /**
+     * @param ListNode $list_head
+     * @param ListNode $list_tail
+     * @return ListNode
+     */
+    private static function set_list_head(?ListNode $list_head, ListNode $list_tail): ListNode {
+        if ($list_head === null) {
+            $list_head = $list_tail;
+        }
+        return $list_head;
+    }
+
+}