1.3.42复制栈。为基于链表产现的栈编写一个新的构造函数,使以下代码Stack<Item> t=new Stack<Item>(s);得到的t指向栈s的一个新的独立的副本。
答:
import java.util.Iterator;
public class Stack<Item> implements Iterable<Item>
{
private int N;
private Node first;
private class Node
{
Item item;
Node next;
}
public Stack()
{
}
public Stack(Stack s)
{
Node right=new Node();
Node oldright;
for(Object i:s)
{
oldright=right;
right=new Node();
right.item=(Item) i;
right.next=null;
if(isEmpty())
first=right;
else
oldright.next=right;
N++;
}
}
public boolean isEmpty()
{return N==0;}
public int size()
{return N;}
public void push(Item item)
{
Node oldfirst=first;
first=new Node();
first.item=item;
first.next=oldfirst;
N++;
}
public Item pop()
{
Item item=first.item;
first=first.next;
N--;
return item;
}
public Item peek()
{
Item item=first.item;
return item;
}
public Iterator<Item> iterator()
{return new ListIterator();}
private class ListIterator implements Iterator<Item>
{
private Node current=first;
public boolean hasNext(){return current!=null;}
public void remove(){}
public Item next()
{
Item item=current.item;
current=current.next;
return item;
}//end next
}//end class ListIterator
public static void main(String[] args)
{
Stack<String> s=new Stack<String>();
while(!StdIn.isEmpty())
{
String item=StdIn.readString();
s.push(item);
} //end while
StdOut.println("---Stack s is:");
for(String i:s)
StdOut.print(i+" ");
Stack<String> t=new Stack<String>(s);
StdOut.println();
StdOut.println("---Stack after new Stack<String>(s) is:");
for(String i:s)
StdOut.print(i+" ");
//
s.pop();
StdOut.println();
StdOut.println("---Stack after s pop, s is:");
for(String i:s)
StdOut.print(i+ " ");
//
StdOut.println();
StdOut.println("---Stack t is:");
for(String i:t)
StdOut.print(i+" ");
}
}