数据结构之-栈（Java实现）

理解

栈是仅在末尾进行插入和删除操作的线性表。具有LIFO(last in first out)的特性。
也就是说，栈是一种特殊的线性表。
点击查看大图

在《大话数据结构》中，作者主要给了两种实现方式：基于数组和基于链表的实现。因为栈是一种特殊的线性表，我们只需要对顺序存储和链式存储做一些修改，只让其操作头部和尾部，就可以达到目的。

基于数组的实现（Java实现）

实现代码

//栈(数组实现)public class MyStack {    //大小    private int size;    //栈的最大容量    private int maxSize;    //默认最大容量为10    private static final int DEFAULT_MAX_SIZE = 10;    //数组（用来保存数据）    String stack[];    public MyStack(int maxSize) {        this.maxSize = maxSize;        stack = new String[maxSize];    }    public MyStack() {        this(DEFAULT_MAX_SIZE);    }    public void push(String s) {        if (size >= maxSize) {            throw new IndexOutOfBoundsException("栈已经满了");        }        stack[size] = s;        size++;        look();    }    public  String pop(){        String rs = stack[size-1];        stack[size-1]=null;        size--;        look();        return rs;    }    public void clear(){        for (int i = 0; i < size; i++) {            stack[i] = null;        }        size=0;        look();    }    public int getSize() {        return size;    }    private void look() {        System.out.println("");        for (int i = 0; i < maxSize; i++) {            System.out.print(stack[i]+" ");        }    }}

演示

public class Main {    public static void main(String[] args) {        MyStack stack = new MyStack(4);        stack.push("1");        stack.push("2");        stack.push("3");        stack.push("4");        stack.pop();        stack.pop();        stack.push("a");        stack.push("b");    }}

结果：

1 null null null 1 2 null null 1 2 3 null 1 2 3 4 1 2 3 null 1 2 null null 1 2 a null 1 2 a b 

基于链表的实现（Java实现）

实现代码

//栈(链表实现)public class MyStackNode {    //栈顶的节点    private Node top;    //大小    private int size;    //栈的最大容量    private int maxSize;    //默认最大容量为10    private static final int DEFAULT_MAX_SIZE = 10;    public MyStackNode(int maxSize) {        this.maxSize = maxSize;    }    public MyStackNode() {        this(DEFAULT_MAX_SIZE);    }    //将数据添加到栈中    public void push(String s) {        if (size >= maxSize) {            throw new IndexOutOfBoundsException("栈已经满了");        }        Node node = new Node(s, top);        top = node;        look();        size++;    }    /**     * 移除栈顶的数据     */    public String pop() {        if (top == null)            return null;        Node oldTop = top;        Node newTop = top.next;        String rs = oldTop.s;        oldTop.next = null;        oldTop.s = null;        oldTop = null;        top = newTop;        look();        size--;        return rs;    }    /**     * 清空栈中的而数据     */    public void clear() {        Node node = top;        while (node != null) {            Node newTop = node.next;            node.next = null;            node.s = null;            node = newTop;        }        look();        size=0;    }    class Node {        public String s;        public Node next;        public Node(String s, Node next) {            this.s = s;            this.next = next;        }        public void setNext(Node next) {            this.next = next;        }    }    //查看数据    private void look(){        System.out.println("");        Node node = top;        while (node != null) {            System.out.print(node.s + " ");            node = node.next;        }    }    public int getSize() {        return size;    }}

演示

public class Main {    public static void main(String[] args) {        MyStackNode stack = new MyStackNode(4);        stack.push("1");        stack.push("2");        stack.push("3");        stack.push("4");        stack.pop();        stack.pop();        stack.push("a");        stack.push("b");    }}

结果（数组实现中查看方式是从底部开始查看，这里是从顶部开始查看，所以视觉顺序不一致）

1 2 1 3 2 1 4 3 2 1 3 2 1 2 1 a 2 1 b a 2 1 

两栈共享空间

这种栈的实现逻辑比较奇怪，为了节约空间而无所不用其极。我看了半天没想明白：为了节约空间，为啥不一开始就把开辟的内存空间尽可能的压缩，却要用这种奇怪的方式来节约空间？这种哲学上的思考就不去深究了，这里给出实现的代码，各位可以参考参考。

实现代码

//两栈共享空间public class ShareStack {    //大小    private int size;    //栈的最大容量    private int maxSize;    //默认最大容量为10    private static final int DEFAULT_MAX_SIZE = 10;    //数组（用来保存数据）    private String[] stack;    private int leftTop = -1;    //右侧栈顶的索引    private int rightTop;    public ShareStack(int maxSize) {        this.maxSize = maxSize;        stack = new String[maxSize];        rightTop = maxSize;    }    public ShareStack() {        this(DEFAULT_MAX_SIZE);    }    public void pushLeft(String s) {        if (leftTop + 1 >= rightTop) {            throw new IndexOutOfBoundsException("栈已经满了");        }        leftTop++;        stack[leftTop] = s;        size++;        look();    }    public void pushRight(String s) {        if (leftTop + 1 >= rightTop) {            throw new IndexOutOfBoundsException("栈已经满了");        }        rightTop--;        stack[rightTop] = s;        size++;        look();    }    public String popLeft() {        if (leftTop == -1)            return null;        String rs = stack[leftTop];        stack[leftTop] = null;        leftTop--;        size--;        look();        return rs;    }    public String popRight() {        if (rightTop == maxSize)            return null;        String rs = stack[rightTop];        stack[rightTop] = null;        rightTop++;        size--;        look();        return rs;    }    public void clearLeft() {        int leftSize = leftTop + 1;        for (int i = 0; i < leftSize; i++) {            stack[i] = null;        }        size = size - leftSize;        leftTop = -1;        look();    }    public void clearRight() {        int rightSize = maxSize - rightTop;        for (int i = maxSize - 1; i >= rightTop; i--) {            stack[i] = null;        }        size = size - rightSize;        rightTop = maxSize;        look();    }    public int getSize() {        return size;    }    private void look() {        System.out.println("");        for (int i = 0; i < maxSize; i++) {            System.out.print(stack[i] + " ");        }    }}

演示

public class Main {    public static void main(String[] args) {        ShareStack stack = new ShareStack(4);        stack.pushLeft("1");        stack.pushLeft("2");        stack.pushLeft("3");        stack.pushLeft("4");        stack.popLeft();        stack.popLeft();        stack.pushRight("a");        stack.pushRight("b");    }}

结果

1 null null null 1 2 null null 1 2 3 null 1 2 3 4 1 2 3 null 1 2 null null 1 2 null a 1 2 b a 

结语

数据结构-线性表之顺序储存（Java实现）和 数据结构-线性表之单链表（Java实现）明白的话，栈是很好实现的；因为栈是一种特殊的线性表

转载请标明出处：http://blog.csdn.net/qq_26411333/article/details/51922484