Java 数据结构-使用数组实现栈


本文摘自JavaGuide。

实现一个,要求这个栈具有 push()、pop()(返回栈顶元素并出栈)、peek() (返回栈顶元素不出栈)、isEmpty()、size()这些基本的方法。

提示:每次入栈之前先判断栈的容量是否够用,如果不够用就用Arrays.copyOf()进行扩容;

public class MyStack {
    private int[] storage;//存放栈中元素的数组
    private int capacity;//栈的容量
    private int count;//栈中元素数量
    private static final int GROW_FACTOR = 2;

    //TODO:不带初始容量的构造方法。默认容量为8
    public MyStack() {
        this.capacity = 8;
        this.storage=new int[8];
        this.count = 0;
    }

    //TODO:带初始容量的构造方法
    public MyStack(int initialCapacity) {
        if (initialCapacity < 1)
            throw new IllegalArgumentException("Capacity too small.");

        this.capacity = initialCapacity;
        this.storage = new int[initialCapacity];
        this.count = 0;
    }

    //TODO:入栈
    public void push(int value) {
        if (count == capacity) {
            ensureCapacity();
        }
        storage[count++] = value;
    }

    //TODO:确保容量大小
    private void ensureCapacity() {
        int newCapacity = capacity * GROW_FACTOR;
        storage = Arrays.copyOf(storage, newCapacity);
        capacity = newCapacity;
    }

    //TODO:返回栈顶元素并出栈
    private int pop() {
        if (count == 0)
            throw new IllegalArgumentException("Stack is empty.");
        count--;
        return storage[count];
    }

    //TODO:返回栈顶元素不出栈
    private int peek() {
        if (count == 0){
            throw new IllegalArgumentException("Stack is empty.");
        }else {
            return storage[count-1];
        }
    }

    //TODO:判断栈是否为空
    private boolean isEmpty() {
        return count == 0;
    }

    //TODO:返回栈中元素的个数
    private int size() {
        return count;
    }

}

验证

MyStack myStack = new MyStack(3);
myStack.push(1);
myStack.push(2);
myStack.push(3);
myStack.push(4);
myStack.push(5);
myStack.push(6);
myStack.push(7);
myStack.push(8);
System.out.println(myStack.peek());//8
System.out.println(myStack.size());//8
for (int i = 0; i < 8; i++) {
    System.out.println(myStack.pop());
}
System.out.println(myStack.isEmpty());//true
myStack.pop();//报错:java.lang.IllegalArgumentException: Stack is empty.

欢迎分享,(木庄网络博客交流QQ群:562366239

打赏

取消

感谢您的支持,我会继续努力的!

扫码支持
扫码打赏,您说多少就多少

打开支付宝扫一扫,即可进行扫码打赏哦

分享从这里开始,精彩与您同在

评论