Java の一般的な線形データ構造とその実装: スタックからキューまでの探索

public class ArrayStack {
    private int[] stack;
    private int top;  // 栈顶指针

    public ArrayStack(int capacity) {
        stack = new int[capacity];
        top = -1;
    }

    public boolean isEmpty() {
        return top == -1;
    }

    public boolean isFull() {
        return top == stack.length - 1;
    }

    public void push(int item) {
        if (isFull()) {
            throw new RuntimeException("Stack is full");
        }
        stack[++top] = item;
    }

    public int pop() {
        if (isEmpty()) {
            throw new RuntimeException("Stack is empty");
        }
        return stack[top--];
    }

    public int peek() {
        if (isEmpty()) {
            throw new RuntimeException("Stack is empty");
        }
        return stack[top];
    }
}

public class LinkedStack {
    private Node top;

    public LinkedStack() {
        top = null;
    }

    public boolean isEmpty() {
        return top == null;
    }

    public void push(int item) {
        Node newNode = new Node(item);
        newNode.next = top;
        top = newNode;
    }

    public int pop() {
        if (isEmpty()) {
            throw new RuntimeException("Stack is empty");
        }
        int item = top.data;
        top = top.next;
        return item;
    }

    public int peek() {
        if (isEmpty()) {
            throw new RuntimeException("Stack is empty");
        }
        return top.data;
    }

    private class Node {
        private int data;
        private Node next;

        public Node(int data) {
            this.data = data;
            this.next = null;
        }
    }
}

public class ArrayQueue {
    private int[] queue;
    private int front;  // 队头指针
    private int rear;  // 队尾指针

    public ArrayQueue(int capacity) {
        queue = new int[capacity + 1];  // 额外预留一个空位
        front = rear = 0;
    }

    public boolean isEmpty() {
        return front == rear;
    }

    public boolean isFull() {
        return (rear + 1) % queue.length == front;
    }

    public void enqueue(int item) {
        if (isFull()) {
            throw new RuntimeException("Queue is full");
        }
        queue[rear] = item;
        rear = (rear + 1) % queue.length;
    }

    public int dequeue() {
        if (isEmpty()) {
            throw new RuntimeException("Queue is empty");
        }
        int item = queue[front];
        front = (front + 1) % queue.length;
        return item;
    }

    public int peek() {
        if (isEmpty()) {
            throw new RuntimeException("Queue is empty");
        }
        return queue[front];
    }
}

public class LinkedQueue {
    private Node front;  // 队头指针
    private Node rear;  // 队尾指针

    public LinkedQueue() {
        front = null;
        rear = null;
    }

    public boolean isEmpty() {
        return front == null;
    }

    public void enqueue(int item) {
        Node newNode = new Node(item);
        if (isEmpty()) {
            front = newNode;
            rear = newNode;
        } else {
            rear.next = newNode;
            rear = newNode;
        }
    }

    public int dequeue() {
        if (isEmpty()) {
            throw new RuntimeException("Queue is empty");
        }
        int item = front.data;
        front = front.next;
        if (front == null) {
            rear = null;
        }
        return item;
    }

    public int peek() {
        if (isEmpty()) {
            throw new RuntimeException("Queue is empty");
        }
        return front.data;
    }

    private class Node {
        private int data;
        private Node next;

        public Node(int data) {
            this.data = data;
            this.next = null;
        }
    }
}