java栈实现

java栈实现

数组实现

Stack类

class Stack {
    private int maxSize;
    private int[] stack;
    private int top = -1;

    public Stack(int maxSize) {
        this.maxSize = maxSize;
        stack = new int[maxSize];
    }

    public void show() {
        if (isEmpty()) {
            System.out.println("栈空的");
            return;
        }
        for (int i = top; i >= 0; --i) {
            System.out.println("stack[" + i + "] ==> " + stack[i]);
        }
    }

    public void push(int value) {
        if (isFull()) {
            System.out.println("栈满了");
            return;
        }
        // 插入数据
        stack[++top] = value;
    }

    public Integer pop() {
        if (isEmpty()) {
            System.out.println("栈是空的");
            return null;
        }
        // pop
        return stack[top--];
    }

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

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

测试类

public class StackDemo {
    public static void main(String[] args) {
        Stack stack = new Stack(3);
        String key = "";
        boolean loop = true;
        Scanner scanner = new Scanner(System.in);
        Scanner numInput = new Scanner(System.in);


        while (loop) {
            System.out.println("show:显示栈");
            System.out.println("push:压元素入栈");
            System.out.println("pop:弹元素出栈");
            System.out.println("exit:退出");

            key = scanner.nextLine();
            switch (key) {
                case "show":
                    stack.show();
                    break;
                case "push":
                    System.out.println("输入一个要压入栈的数");
                    int num = numInput.nextInt();
                    stack.push(num);
                    break;
                case "pop":
                    System.out.println(stack.pop());
                    break;
                case "exit":
                    scanner.close();
                    numInput.close();
                    System.exit(0);
                    break;
                default:
                    System.out.println("输入不合法");
                    break;
            }
        }
    }
}

---

链表实现

节点类

class Node {
    public int id;
    public Node pre;
    public Node next;

    public Node(int id) {
        this.id = id;
    }

    @Override
    public String toString() {
        return "Node{" +
                "id=" + id +
                ", next=" + next +
                '}';
    }
}

Stack类

class LinkedListStack {
    private Node head = new Node(0);
    private Node top = new Node(0);

    public void show() {
        if (isEmpty()) {
            System.out.println("栈空");
            return;
        }
        Node tem = top.next;
        while (true) {
            if (tem == head) {
                break;
            }
            System.out.println(tem);
            tem = tem.pre;
        }
    }

    public Node pop() {
        if (isEmpty()) {
            System.out.println("栈空");
            return null;
        }
        Node tem = top.next;
        top.next = null;
        top = top.pre;
        return tem;
    }

    public void push(Node node) {
        Node tem = head;
        while (true) {
            if (tem.next == null) {
                break;
            }
            // 移动tem
            tem = tem.next;
        }
        // push并移动top
        tem.next = node;
        node.pre = tem;
        top = tem;
    }

    private boolean isEmpty() {
        return (head.next == null);
    }
}

---

测试类

public class StackDemo {
    public static void main(String[] args) {
        LinkedListStack linkedListStack = new LinkedListStack();
        linkedListStack.push(new Node(0));
        linkedListStack.push(new Node(1));
        linkedListStack.push(new Node(2));
        linkedListStack.pop();
        linkedListStack.show();
    }
}