Java语言实现数据结构栈代码详解

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。

首先了解下栈的概念：

栈是限定仅在表头进行插入和删除操作的线性表。有时又叫LIFO（后进先出表）。要搞清楚这个概念，首先要明白”栈“原来的意思，如此才能把握本质。

"栈“者,存储货物或供旅客住宿的地方,可引申为仓库、中转站，所以引入到计算机领域里，就是指数据暂时存储的地方，所以才有进栈、出栈的说法。

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;

public interface Stack {
	
	Boolean isEmpty();
	
	void clear();
	
	T pop();
	
	Boolean push(T data);
	
	int length();
	
	T peek();
	
	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;

public class LinearStack implements Stack {
	@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];
		}
	}
	
	@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;
	}
	
	@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 implements Stack {
	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。

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