Question

有人知道如何编写递归打印堆栈的toStringRec方法吗？下面是类和主要方法文件我已经尝试了几个小时来运行它，但未能完成它。

public class IntLinkedStack
{
private IntNode top;
public static int temp = 0;

public boolean isEmpty()
{
    if (top == null)
    return true;
    else
    return false;
}

public int size()
{
    return sizeRec(top);
}
private int sizeRec(IntNode t)
{

    IntNode aux = t;

    if (aux != null){
        temp++;
        sizeRec(aux.next);
    }

    return temp ;

}

public String toString()
{
    return toStringRec(top);
}

// WRITE THIS METHOD:  toStringRec
private String toStringRec(IntNode t)
{        

}

public int peek()
{
    if (isEmpty())
    throw new RuntimeException("Peek attempted on empty stack");
    else
    return top.data;
}

public void push(int m)
{
    IntNode temp;
    temp = new IntNode();
    temp.data = m;

    temp.next = top;
    top = temp;
}

public int pop()
{
    int value;

    if (isEmpty())
    throw new RuntimeException("Pop attempted on empty stack");
    else
    {
        value = top.data;
        top = top.next;
        return value;
    }
}

}

接下来是主要方法

import java.util.Scanner;

public class ITDIntLinkedStack
{
public static void displayMenu()
{
System.out.println("\n(1) display menu");
System.out.println("(2) check isEmpty");
System.out.println("(3) push");
System.out.println("(4) peek");
System.out.println("(5) pop");
System.out.println("(6) empty the stack");
System.out.println("(7) size");
System.out.println("(8) toString");
System.out.println("(0) quit");
}

public static void main(String [] args)
{
if (true || false)
  System.out.println("YES");



Scanner kbd = new Scanner(System.in);
IntLinkedStack x = new IntLinkedStack();
int choice = 1;
int value;

System.out.println("Here are your choices: ");
displayMenu();

System.out.print("\nEnter your choice#:  ");
  choice = kbd.nextInt();

while (choice >= 1 && choice <= 8)
{
  if (choice == 1)
    displayMenu();
  else if (choice == 2)
    System.out.println("Stack isEmpty?:  " + x.isEmpty() );
  else if (choice == 3)
  {
    System.out.print("Enter value to push:  ");
    value = kbd.nextInt();
    x.push(value);
    System.out.println("Pushed value " + value + ".");
  }
  else if (choice == 4)
  {
    value = x.peek();
    System.out.println("Peeked at top of stack:  " + value + ".");
  }
  else if (choice == 5)
  {
    value = x.pop();
    System.out.println("Popped " + value + " off the stack.");
  }

  else if (choice == 6)
  {
    System.out.println("Emptying stack...");
    while (!x.isEmpty())
      System.out.println("Popped " + x.pop());
    System.out.println("Stack is now emptied.");
  }

  else if (choice == 7)
    System.out.println("Size is " + x.size());

  else if (choice == 8)
  {
    System.out.println("Here is a view of the stack: ");
    System.out.println(x.toString());
  }


  System.out.print("\nEnter your choice#:  ");
  choice = kbd.nextInt();

}  // end while (choice >= 1 && <= 9)

System.out.println("Bye!");

 } // end public static void main(String [] args)


} // end public class ITDArrayStack

Answer 1

递归打印堆栈元素：

  private String toStringRec(IntNode t) {
    if (t == null)
      return "";
    return t.data + "\n" + toStringRec(t.next);
  }

递归堆栈打印方法

1 个答案: