多项式 String s 成双向链表？解析必须完成，我们必须找到系数和

Question

大家好，所以我必须弄清楚如何在多项式构造函数中获取 (String s) 并将其放入双向链表中？创建一个术语。 然后将表达式分解为各个部分并为每个部分创建术语。 这些需要组合和重新排序以将它们转换为规范形式并存储在 DList 中。 解析必须在之后进行。我们需要使用双向链表实现来进行规范化或操作输入字符串，然后存储在链表中。

public class Polynomial extends AbstractPolynomial { 
public Polynomial(String s) { // complete this code
This I will have to parse eventually and bring create a node
        

/* This is what I've done so far so I'm trying to go through String and look for the - + and then get the index?  */
    
    int [] coef;
    int degree;
    int d = -1;

        for (int i = 0; i < s.length(); i++) {
 
            if(s.charAt(i)=='-') {

            }
          if(s.charAt(i)== '+'){

          }
//All the way to here

        }


    }



    public Polynomial() { //we don't touch or modify
        super();
    }

    public AbstractPolynomial add(AbstractPolynomial p){ 
        AbstractPolynomial ans = new Polynomial();

        // complete this code
        return ans;
    }

    public AbstractPolynomial subtract(AbstractPolynomial p) { 
        AbstractPolynomial ans = new Polynomial();
        // complete this code
        return ans;
    }

    public AbstractPolynomial multiply(AbstractPolynomial p) { //we have to multiply
        AbstractPolynomial ans = new Polynomial();
        // complete this code
        return ans;
    }

    /****************
     * MAIN FUNCTION
     ****************/

    public static void main(String args[]) throws Exception {//we don't touch or modify
        //Variables
        Scanner scnr = new Scanner(System.in);
        AbstractPolynomial p, q;
        String testInput = "";
        //Custom test case
        if(scnr.hasNext()){
            testInput = scnr.nextLine();
            p = new Polynomial(testInput);
            testInput = scnr.nextLine();
            q = new Polynomial(testInput);
            System.out.println("User Input\n***************************");
            Utility.run(p, q);
        }
        //Default test case
        else{
            p = new Polynomial(" X^5");
            q = new Polynomial("X^2 - X + 1");
            System.out.println("Default Input\n***************************");
            Utility.run(p, q);
        }
    }
}

class Term {     // we don't touch or modify

    Double coefficient;
    int degree;

    public Term() {
        this(null, 0);
    }
    public boolean isPositive() {
        return coefficient > 0;
    }
    public Term(Double coefficient, int degree) {//we don't touch or modify
        this.coefficient = coefficient;
        this.degree = degree;
    }
    public Double getCoefficient() {//we don't touch or modify
        return coefficient;
    }
    public void setCoefficient(Double coefficient) {//we don't touch or modify
        this.coefficient = coefficient;
    }
    public int getDegree() {//we don't touch or modify
        return degree;
    }
    public void setDegree(int degree) {//we don't touch or modify
        this.degree = degree;
    }
    public String toString() {//we don't touch or modify
        String ans = "";
        if (coefficient.doubleValue() == 0) return "";
        if (degree == 0) return coefficient.toString();
        if (coefficient != 1) {
            if (coefficient == -1) ans += "-";
            else ans += coefficient + " ";
        }
        ans = ans + "X";
        if (degree == 1) return ans;
        return ans + "^" + degree;
    }
}
class DList<T> {//we don't touch or modify

    private DNode<T> header, trailer;
    private int size;

    public DList() {
        size = 0;
        header = new DNode<T>(null, null, null);
        trailer = new DNode<T>(null, header, null);
        header.setNext(trailer);
    }

    // utility methods

    public int size() {//we don't touch or modify
        return size;
    }

    public boolean isEmpty() {//we don't touch or modify
        return size == 0;
    }

    // give clients access to nodes, but not to the header or trailer

    public DNode<T> getFirst() throws Exception {//we don't touch or modify
        if (isEmpty())
            throw new Exception("Empty");
        return header.getNext();
    }

    public DNode<T> getLast() throws Exception {//we don't touch or modify
        if (isEmpty())
            throw new Exception("Empty");
        return trailer.getPrev();
    }

    public DNode<T> getNext(DNode<T> v) throws Exception {//we don't touch or modify
        DNode<T> ans = v.getNext();
        if (ans == null || ans == trailer)
            throw new Exception("No such node");
        return ans;
    }

    public DNode<T> getPrev(DNode<T> v) throws Exception {//we don't touch or modify
        DNode<T> ans = v.getPrev();
        if (ans == null || ans == header)
            throw new Exception("No such node");
        return ans;
    }

    // methods to change the list

    public void addBefore(T d, DNode<T> v) {//we don't touch or modify
        DNode<T> u = v.getPrev();
        DNode<T> x = new DNode<T>(d, u, v);
        u.setNext(x);
        v.setPrev(x);
        size++;
    }

    public void addAfter(T d, DNode<T> v) {//we don't touch or modify
        DNode<T> w = v.getNext();
        DNode<T> x = new DNode<T>(d, v, w);
        v.setNext(x);
        w.setPrev(x);
        size++;
    }

    public void addFirst(T d) {//we don't touch or modify
        addAfter(d, header);
    }

    public void addLast(T d) {//we don't touch or modify
        addBefore(d, trailer);
    }

    public T remove(DNode<T> v) throws Exception {//we don't touch or modify
        if (v == header || v == trailer)
            throw new Exception("Sentinel");
        DNode<T> u = v.getPrev();
        DNode<T> w = v.getNext();
        w.setPrev(u);
        u.setNext(w);
        size--;
        return v.getData();
    }

    // LinkedList testing methods:

    public String toString() {//we don't touch or modify
        String ans = "";
        DNode<T> n = header;
        ans += "(H)<-->";
        do {
            n = n.getNext();
            if (n == trailer)
                ans += "(T)";
            else
                ans += (n.getData() + "<-->");
        } while (n != trailer);
        return ans;
    }
}
abstract class AbstractPolynomial { //we don't touch or modify

    DList<Term> data = null;
    public AbstractPolynomial() {
        data = new DList<>();
    }
    public final String toString() {
        String ans = "";
        boolean starting = true;
        try {
            DNode<Term> n = data.getFirst();
            while (n != null) {
                if (!starting && n.getData().isPositive()) ans += " +";
                starting = false;
                ans += " " + n.getData().toString();
                n = data.getNext(n);
            }
        } catch (Exception e) {
            if (starting) return "0";
        }
        return ans;
    }
    abstract public AbstractPolynomial add(AbstractPolynomial p);
    abstract public AbstractPolynomial subtract(AbstractPolynomial p);
    abstract public AbstractPolynomial multiply(AbstractPolynomial p);
}

class Utility {// we don't touch or modify


    public static void run(AbstractPolynomial p, AbstractPolynomial q) throws Exception {//dont touch or modify
        System.out.println("Polynomials\np = " + p + "\nq = " + q);
        System.out.println("Sum " + p.add(q));
        System.out.println("Difference " + p.subtract(q));
        System.out.println("Product " + p.multiply(q));
    }
}
class DNode<T> { //we don't touch or modify
    private T data;
    private DNode<T> prev, next;

    public DNode(T d, DNode<T> p, DNode<T> n) {
        data = d;
        next = n;
        prev = p;
    }

    public T getData() {
        return data;
    }

    public DNode<T> getNext() {
        return next;
    }
}

Answer 1

如果你需要将输入作为一个字符串进行分离，你应该尝试使用String类中的split()方法。

https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split(java.lang.String)