# 用链表实现栈

对链表使用头插法，后添加的元素一直位于链表头部。

```
public class LinkedStack implements Stack {

    //使用空头结点简化相关操作
    private Node top = new Node(Integer.MAX_VALUE);
    private int size = 0;
    private int initCap;

    public LinkedStack(int initCap) {
        this.initCap = initCap;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    @Override
    public int pop() {
        if (isEmpty()) {
            return -1;
        }
        Node popNode = top.next;
        top.next = popNode.next;
        popNode.next = null;
        size--;
        return popNode.data;
    }

    @Override
    public boolean push(int data) {
        if (size == initCap) {
            return false;
        }
        Node newNode = new Node(data);
        newNode.next = top.next;
        top.next = newNode;
        size++;
        return true;
    }

    @Override
    public int size() {
        return size;
    }

    @Override
    public void clear() {
        //清理数据
        while (top.next != null) {
            Node n = top.next;
            top.next = n.next;
            n.next = null;
        }
        size = 0;
    }


    static class Node {
        Node(int data) {
            this.data = data;
        }

        int data;
        Node next;
    }
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://wenhaiz.gitbook.io/kx-android/computer_science/datastructure/stack/xiang-guan-suan-fa-ti-mu/linked_stack.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.