java - 在链表中表示多项式

我需要在类中表示一个多项式：


  PolyNode（带有下一个变量）：
  
  
  int _power
  双系数
  PolyNode _next
  
  
  多项式（以及下一个构造函数和方法）：
  
  
  公共Polynom（）-空构造函数-空列表
  公共Polynom（PolyNode p）-从PolyNode获取参数并将其作为列表的第一位插入
  公共Polynom addNode（PolyNode p）-从PolyNode获取参数并将其添加到Polynom。并返回新的多项式
  


这是测试用例：

   // Create two Polynoms
    Polynom p1 = new Polynom();
    p1.addNode(new PolyNode(0,2));
    p1.addNode(new PolyNode(2,4));
    System.out.println("\nP1:");
    System.out.println(p1);

    Polynom p2 = new Polynom(new PolyNode(0,2));
    p2.addNode(new PolyNode(2,-1));
    p2.addNode(new PolyNode(4,5));
    System.out.println("\nP2:");
    System.out.println(p2);

这是所需的输出：


  P1：
  4.0x ^ 2 + 2.0
  
  P2：
  5.0x ^ 4-1.0x ^ 2 + 2.0


那就是我写的PolyNode类：

public class PolyNode
{
     char _operation;
     int _power;
     double _coefficient;
     PolyNode _next;



     public PolyNode()
{
  _next = null;
  _operation = '+';
  _coefficient = 1;
  _power = 1;
}

  public PolyNode(char oper, double coeff, int power, PolyNode next)
{
  _operation = oper;
  _coefficient = coeff;
  _power = power;
  _next = next;
}


public PolyNode(PolyNode next)
{
  _next = next;
}

public PolyNode(int power, int coeff)
{
_power = power;
  _coefficient = coeff;
}

public void setSign(char oper)
{
  _operation = oper;
}


public void setCoef(double coeff)
{
  _coefficient = coeff;
}


public void setPower(int power)
{
  _power = power;
}


public void setNext(PolyNode next)
{
  _next = next;
}


public char getSign()
{
  return _operation;
}


public double getCoeff()
{
  return _coefficient;
}

  public int getPower()
{
  return _power;
}

public PolyNode getNext()
{
  return _next;
}

public boolean isEnd()
{
  return (_next == null);
}

}

那就是我写的Polynom类：

public class Polynom
{
    private PolyNode _head;


    public Polynom ()
    {
        _head = null;
    }

        public Polynom (Polynom poly)
    {
        Polynom r = new Polynom (poly);
    }

    public Polynom (PolyNode p)
    {
        _head = p;
    }

    public Polynom addNode (PolyNode p)
    {
        Polynom r = new Polynom (p);
        PolyNode current;

        if (_head == null)
              _head = p;

         else
         {
             current = _head;
             while (current._next !=null)
                current = current._next;
                current._next = p;

            }
                return r;
        }

        public String toString()
        {
            String s = "";

            while (_head != null)
            {
            s += _head.getCoeff() + "x^" + _head.getPower();
           _head = _head._next;
        }

            return s;

        }
    }

这是我的错误输出：


  P1：
  2.0x ^ 04.0x ^ 2
  
  P2：
  2.0x ^ 0-1.0x ^ 25.0x ^ 4


我不明白链表的概念！

toString()方法需要像这样的示例输出：


  r = 3.8x10-5.9x3 + 5.5x2-11.0


将在toString（）上显示为：


  3.8 x ^ 10 – 5.9 x ^ 3 + 5.5 x ^ 2 – 11.0

最佳答案

我想如果您有一个PolyNode的toString（）方法会容易一些，而Polynom会在列表中有一个节点的同时调用该方法。

您要处理的唯一“特殊”情况是列表的开头，如果该词为正数，则您不想打印“ +”号。

除此之外，您的toString（）实现中还存在一些问题，尤其是在迭代列表时：

public String toString(){
    StringBuffer s = new StringBuffer();
    // WARNING: you don't want to use the list head for iteration,
    // otherwise you lose the reference to it, and basically to the whole list!
    PolyNode current = _head; // so we use a cursor node reference
    while (current.next!=null){ // while current is not the last node
        // you want to have the sign first, for every node,
        // except the first, if it's positive
        if(current!=_head || current.getSign()=='-')
            s.append(current.getSign() + " ");
        // then you append the coefficient
        s.append(current.getCoeff());
        // and then the exponent
        s.append(" x^" + current.getPower() + " ");
        // you keep going to the next node
        current = current._next;
    }
    return s.toString();
}

我建议您在深入练习之前，先看一下链表的一些实现以了解链表。