数据结构栈的java实现

近来复习数据结构，自己动手实现了栈。栈是一种限制插入和删除只能在一个位置上的表。最基本的操作是进栈和出栈，因此，又被叫作“先进后出”表。

实现方式是这样的：首先定义了一个接口，然后通过这个接口实现了线性栈和链式栈，代码比较简单，如下：

 package com.peter.java.dsa.interfaces;

 /**
  * 栈操作定义
  *
  * @author Peter Pan
  */

 public interface Stack<T> {
     /* 判空 */
     boolean isEmpty();

     /* 清空栈 */
     void clear();

     /* 弹栈 */
     T pop();

     /* 入栈 */
     boolean push(T data);

     /* 栈的长度 */
     int length();

     /* 查看栈顶的元素，但不移除它 */
     T peek();

     /* 返回对象在栈中的位置 */
     int search(T data);
 }

线性栈：以数组的方式实现。

 package com.peter.java.dsa.common;

 import com.peter.java.dsa.interfaces.Stack;

 /**
  * 线性栈
  *
  * @author Peter Pan
  */
 public class LinearStack<T> implements Stack<T> {
     @SuppressWarnings("unchecked")
     private T[] t = (T[]) new Object[16];
     private int size = 0;

     @Override
     public boolean isEmpty() {
         // TODO Auto-generated method stub
         return size == 0;
     }

     @Override
     public void clear() {
         // TODO Auto-generated method stub
         for (int i = 0; i < t.length; i++) {
             t[i] = null;
         }
         size = 0;
     }

     @Override
     public T pop() {
         // TODO Auto-generated method stub
         if (size == 0) {
             return null;
         }
         T tmp = t[size - 1];
         t[size - 1] = null;
         size--;
         return tmp;
     }

     @Override
     public boolean push(T data) {
         // TODO Auto-generated method stub
         if (size >= t.length) {
             resize();
         }
         t[size++] = data;
         return true;
     }

     @Override
     public int length() {
         // TODO Auto-generated method stub
         return size;
     }

     @Override
     public T peek() {
         // TODO Auto-generated method stub
         if (size == 0) {
             return null;
         } else {
             return t[size - 1];
         }
     }

     /* return index of data, return -1 if no data */
     @Override
     public int search(T data) {
         // TODO Auto-generated method stub
         int index = -1;
         for (int i = 0; i < t.length; i++) {
             if (t[i].equals(data)) {
                 index = i;
                 break;
             }
         }
         return index;
     }

     @SuppressWarnings("unchecked")
     private void resize() {
         T[] tmp = (T[]) new Object[t.length * 2];
         for (int i = 0; i < t.length; i++) {
             tmp[i] = t[i];
             t[i] = null;
         }
         t = tmp;
         tmp = null;
     }

     /* from the left to the right is from the top to the bottom of the stack */
     @Override
     public String toString() {
         // TODO Auto-generated method stub
         StringBuffer buffer = new StringBuffer();
         buffer.append("Linear Stack Content:[");
         for (int i = t.length - 1; i > -1; i--) {
             buffer.append(t[i].toString() + ",");
         }
         buffer.append("]");
         buffer.replace(buffer.lastIndexOf(","), buffer.lastIndexOf(",") + 1, "");
         return buffer.toString();
     }

 }

链式栈：通过单链表进行实现。

 package com.peter.java.dsa.common;

 import com.peter.java.dsa.interfaces.Stack;

 public class LinkedStack<T> implements Stack<T> {
     private Node top;
     private int size;

     @Override
     public boolean isEmpty() {
         // TODO Auto-generated method stub
         return size == 0;
     }

     @Override
     public void clear() {
         // TODO Auto-generated method stub
         top = null;
         size = 0;
     }

     @Override
     public T pop() {
         // TODO Auto-generated method stub
         T topValue = null;
         if (top != null) {
             topValue = top.data;
             Node oldTop = top;
             top = top.prev;
             oldTop.prev = null;
             size--;
         }
         return topValue;
     }

     @Override
     public boolean push(T data) {
         // TODO Auto-generated method stub
         Node oldTop = top;
         top = new Node(data);
         top.prev = oldTop;
         size++;
         return true;
     }

     @Override
     public int length() {
         // TODO Auto-generated method stub
         return size;
     }

     @Override
     public T peek() {
         // TODO Auto-generated method stub
         T topValue = null;
         if (top != null) {
             topValue = top.data;
         }
         return topValue;
     }

     @Override
     public int search(T data) {
         // TODO Auto-generated method stub
         int index = -1;
         Node tmp = top;
         for (int i = size - 1; i > -1; i--) {
             if (tmp.data.equals(data)) {
                 index = i;
                 break;
             } else {
                 tmp = tmp.prev;
             }
         }
         tmp = null;
         return index;
     }

     @Override
     public String toString() {
         // TODO Auto-generated method stub
         StringBuffer buffer = new StringBuffer();
         buffer.append("Linked Stack Content:[");
         Node tmp = top;
         for (int i = 0; i < size - 1; i++) {
             buffer.append(tmp.toString() + ",");
             tmp = tmp.prev;
         }
         tmp = null;
         buffer.append("]");
         buffer.replace(buffer.lastIndexOf(","), buffer.lastIndexOf(",") + 1, "");
         return super.toString();
     }

     private class Node {
         T data;
         Node prev;

         public Node(T data) {
             // TODO Auto-generated constructor stub
             this.data = data;
         }
     }

 }

学习还在进行中，以后会继续更新代码。