我正在使用 String Tokenizer 和 Linked Lists,并且此作业需要 Linked Lists。有很多行多项式(每行一个)的外部文件。使用字符串标记器和链表,我正在运行一个 while 循环,它在每次传递时捕获两行并将它们添加到链表中。将数字加载到链表后,目标是将这些多项式从它们的链表中添加在一起,并创建一个包含该多项式的新链表。

例如,文件中的前两行是这样的:

2x^4 -5x^3 +9x^2 -10

3x^4 -6x^3 +10x^2 -11

=
5x^4 -11x^3 +19x^2 -21

这是我的代码:

public class PolynomialAddition
{
    static File dataInpt;
    static Scanner inFile;

    public static void main(String[] args) throws IOException
    {
      dataInpt=new File("C:\\llpoly.txt");
      inFile=new Scanner(dataInpt);
      StringTokenizer myTokens;
      String line,polyTerm;
      Node firstL=new Node();
      Node secondL=new Node();
      line=inFile.nextLine();
      myTokens=new StringTokenizer(line);
      polyTerm=myTokens.nextToken();
      firstL.value=polyTerm.substring(0,polyTerm.indexOf("x"));
      firstL.value2=polyTerm.substring(polyTerm.indexOf("^")+1);

    }
}

这是我的节点类:
public class Node
{
  public Object value;
  public Object value2;
  public Node next;

  public Node()
  {
    value=null;
    value2=null;
    next=null;
  }
  public Node (Object value, Object value2, Node next)
  {
    this.value=value;
    this.value2=value2;
    this.next=next;
  }
}

问题出现在此之后,其中某些行不完整,而它们必须添加到的行是完整的,例如 -12x^8 +5x^2 -3 和 8x^3 +2x

答案应该是 -12x^8 +8x^3 +5x^2 +2x -3

我能做些什么来解决这个问题?

最佳答案

好吧,经过长时间的聊天,这就是“我们”想出来的。我意识到这在某种程度上只是在脱口而出答案。

即便如此,在简洁风格的 Java 1.4 代码中有一个可靠的实现可以帮助您理解很多。

特别注意以表格形式打印结果,在其各自指数的列中对齐不同操作数的项。

代码

有两个文件:

节点.java

class Node {
    int factor;
    int exponent;
    Node next;

    public Node() {
        factor = 0;
        exponent = 0;
        next = null;
    }

    public Node(int factor, int exponent, Node next) {
        this.factor = factor;
        this.exponent = exponent;
        this.next = next;
    }

    public String toString() {
        return String.format("%+4dx^%d    ", new Integer[] { new Integer(factor), new Integer(exponent) });
    }
 }

多项式加法
import java.io.*;
import java.util.*;

public class PolynomialAddition {
    static File dataInpt;
    static Scanner inFile;

    public static void main(String[] args) throws IOException {
        dataInpt = new File("/tmp/input.txt");
        inFile = new Scanner(dataInpt);

        while (inFile.hasNextLine()) {
            Node first = readPolynomial();
//          printList(first);

            Node second = readPolynomial();
//          printList(second);

            Node addition = addPolynomials(first, second);
//          printList(addition);

            printTabulated(first, second, addition);

            System.out.println("\n");
        }
    }

    private static Node addPolynomials(Node first, Node second) {
        Node head = null, current = null;
        while (null!=first || null!=second)
        {
            boolean pickfirst = false;
            boolean haveBoth = (null!=first && null!=second);

            Node node;
            if (haveBoth && first.exponent == second.exponent)
            {
                node = new Node(first.factor + second.factor, first.exponent, null);
                first = first.next;
                second = second.next;
            } else
            {
                pickfirst = first!=null &&
                    ((second == null) || first.exponent > second.exponent);

                if (pickfirst)
                {
                    node = new Node(first.factor, first.exponent, null);
                    first = first.next;
                } else
                {
                    node = new Node(second.factor, second.exponent, null);
                    second = second.next;
                }
            }

            if (current == null)
            {
                head = node;
                current = head;
            } else
            {
                current.next = node;
                current = node;
            }
        }

        return head;
    }

    private static void printTabulated(Node first, Node second, Node addition) {
        String line1="", line2="", barline="", line3="";
        while (addition != null)
        {
            String
                 part1 = "           ",
                 part2 = "           ",
                 part3 = "           ";

            if (null!=first && first.exponent == addition.exponent)
            {
                part1 = first.toString();
                first = first.next;
            }
            if (null!=second && second.exponent == addition.exponent)
            {
                part2 = second.toString();
                second = second.next;
            }
            part3 = addition.toString();
            addition = addition.next;

            line1 += part1;
            line2 += part2;
            barline += "-----------";
            line3 += part3;
        }

        System.out.println(line1);
        System.out.println(line2);
        System.out.println(barline);
        System.out.println(line3);
    }

    private static Node readPolynomial() {
        String line = inFile.nextLine();
        StringTokenizer myTokens = new StringTokenizer(line);

        Node head = null, previous = null;
        while (myTokens.hasMoreTokens()) {
            Node current = new Node();
            String term = myTokens.nextToken();

            if (term.startsWith("+"))
                term = term.substring(1);

            current.factor = Integer.parseInt(
                    term.substring(0, term.indexOf("x")));
            current.exponent = Integer.parseInt(
                    term.substring(term.indexOf("^") + 1));

            if (previous == null)
            {
                head = current;
                previous = head;
            } else
            {
                previous.next = current;
                previous = current;
            }
        }
        return head;
    }

    private static void printList(Node head) {
        for (Node ptr = head; ptr != null; ptr = ptr.next)
            System.out.print(ptr);
        System.out.println();
    }
}

样本数据:

输入:
2x^4 -5x^3 +9x^2 -10x^0
 3x^4 -6x^3 +10x^2 -11x^0
 -2x^1 +4x^0
 2x^1 -4x^0
 8x^5 +6x^4 +5x^2 -3x^0
 -12x^8 +2x^7 +14x^5
 1x^5 +7x^2 +8x^1
 -5x^4 -7x^3 -4x^2 -3x^0
 10x^5 -3x^3 +4x^2 -234x^1 -12x^0
 -5x^5 -2x^3 +10x^0

输出:
  +2x^4      -5x^3      +9x^2     -10x^0
  +3x^4      -6x^3     +10x^2     -11x^0
--------------------------------------------
  +5x^4     -11x^3     +19x^2     -21x^0


  -2x^1      +4x^0
  +2x^1      -4x^0
----------------------
  +0x^1      +0x^0


                        +8x^5      +6x^4      +5x^2      -3x^0
 -12x^8      +2x^7     +14x^5
------------------------------------------------------------------
 -12x^8      +2x^7     +22x^5      +6x^4      +5x^2      -3x^0


  +1x^5                            +7x^2      +8x^1
             -5x^4      -7x^3      -4x^2                 -3x^0
------------------------------------------------------------------
  +1x^5      -5x^4      -7x^3      +3x^2      +8x^1      -3x^0


 +10x^5      -3x^3      +4x^2    -234x^1     -12x^0
  -5x^5      -2x^3                           +10x^0
-------------------------------------------------------
  +5x^5      -5x^3      +4x^2    -234x^1      -2x^0

10-07 19:32
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