PHP Data Structure: The Dance of Stacks and Queues, Understand the Mysteries of Storage and Retrieval

The stack follows last-in-first-out (LIFO), and the elements placed later are taken first. The queue follows first-in, first-out (FIFO), and the elements placed first are taken first. Stacks can be used for backtracking algorithms, while queues can be used for task queues.

PHP Data Structure: Dance of Stack and Queue, Understand the Mysteries of Storage and Retrieval

Data structure is the foundation of computer science. It defines the way data is organized and stored in computer memory. Today, we’ll take a deep dive into two fundamental data structures: stacks and queues, which play a crucial role in real-world applications.

Stack: Last in first out (LIFO)

The stack is like a spring. When you put something in it, the last item put in will be the first one. Items being taken out. This feature is called last-in-first-out (LIFO).

Implementation stack:

class Stack {
    private $items = [];

    public function push($item) {
        array_push($items, $item);
    }

    public function pop() {
        return array_pop($items);
    }

    public function isEmpty() {
        return empty($items);
    }
}

// 创建并操作栈
$stack = new Stack();
$stack->push('A');
$stack->push('B');
echo $stack->pop(); // 输出 'B'
echo $stack->pop(); // 输出 'A'

Queue: first in, first out (FIFO)

The queue is like a queue, inside Those who come first are served first. This feature is called first-in, first-out (FIFO).

Implement queue:

class Queue {
    private $items = [];

    public function enqueue($item) {
        array_push($items, $item);
    }

    public function dequeue() {
        if (empty($items)) {
            return null;
        }
        return array_shift($items);
    }

    public function isEmpty() {
        return empty($items);
    }
}

// 创建并操作队列
$queue = new Queue();
$queue->enqueue('A');
$queue->enqueue('B');
echo $queue->dequeue(); // 输出 'A'
echo $queue->dequeue(); // 输出 'B'

Practical case:

• Stack: Backtracking algorithm The stack is used to store function calls so that they can be returned when needed.
• Queue: Queues are used in task queues to store tasks waiting to be processed, and are processed one by one in first-in, first-out order.

By understanding the data structures of stacks and queues, you can build efficient methods for storing and retrieving data. Mastering these fundamentals will help you solve complex storage and retrieval needs when working on a variety of real-world applications.

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