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<?php |
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declare(strict_types=1); |
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namespace leetcode; |
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use leetcode\util\ListNode; |
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class DesignLinkedList |
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{ |
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private int $size; |
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private ?ListNode $head; |
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/** |
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* Initialize your data structure here. |
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*/ |
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public function __construct() |
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{ |
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$this->size = 0; |
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$this->head = null; |
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} |
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/** |
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* Get the value of the index-th node in the linked list. |
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* If the index is invalid, return -1. |
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* |
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* @param int $index |
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* |
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* @return int |
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*/ |
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public function get(int $index): int |
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{ |
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if ($index < 0 || $index >= $this->size) { |
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return -1; |
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} |
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$curr = $this->head; |
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for ($i = 0; $i < $index; $i++) { |
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$curr = $curr->next; |
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} |
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return $curr->val; |
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} |
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/** |
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* Add a node of value val before the first element of the linked list. |
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* After the insertion, the new node will be the first node of the linked list. |
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* |
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* @param int $val |
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* |
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* @return null |
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*/ |
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public function addAtHead(int $val): void |
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{ |
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$this->addAtIndex(0, $val); |
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} |
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/** |
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* Append a node of value val to the last element of the linked list. |
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* |
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* @param int $val |
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* |
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* @return null |
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*/ |
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public function addAtTail($val): void |
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{ |
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$this->addAtIndex($this->size, $val); |
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} |
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/** |
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* Add a node of value val before the index-th node in the linked list. |
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* If index equals to the length of linked list, |
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* the node will be appended to the end of linked list. |
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* If index is greater than the length, the node will not be inserted. |
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* |
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* @param int $index |
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* @param int $val |
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* |
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* @return null |
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*/ |
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public function addAtIndex(int $index, int $val): void |
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{ |
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if ($index > $this->size) { |
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return; |
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} |
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$node = new ListNode($val); |
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$curr = $this->head; |
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if ($index <= 0) { |
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$node->next = $curr; |
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$this->head = $node; |
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} else { |
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for ($i = 0; $i < $index - 1; $i++) { |
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$curr = $curr->next; |
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} |
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$node->next = $curr->next; |
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$curr->next = $node; |
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} |
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$this->size++; |
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} |
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/** |
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* Delete the index-th node in the linked list, if the index is valid. |
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* |
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* @param int $index |
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* |
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* @return null |
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*/ |
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public function deleteAtIndex(int $index): void |
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{ |
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if ($index < 0 || $index >= $this->size) { |
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return; |
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} |
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$curr = $this->head; |
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if ($index === 0) { |
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$this->head = $curr->next; |
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} else { |
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for ($i = 0; $i < $index - 1; $i++) { |
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$curr = $curr->next; |
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} |
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$curr->next = $curr->next->next; |
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} |
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$this->size--; |
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} |
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} |
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imajinyun /
leetcode-php
