Question

我的乘法逻辑在某处不正确。似乎我没有考虑到我必须添加两个多项式乘以相同程度的项。

public Polynomial multiply(Polynomial p) {
    if (p.poly == null || this.poly == null) {
        Polynomial zero = new Polynomial();
        zero.poly = new Node (0, 0, null);
        return zero;
    } else {

        Polynomial retPol = new Polynomial();
        retPol.poly = new Node(0, 0, null);

        Node front = retPol.poly;
        Node entered = p.poly;
        Node thisPol = this.poly;

        int high = Integer.MIN_VALUE;
        int low = Integer.MAX_VALUE;

        while (entered != null) {
            thisPol = this.poly; 

            while (thisPol != null) {
                if (thisPol.term.degree + entered.term.degree > high)
                    high = thisPol.term.degree + entered.term.degree;
                if (thisPol.term.degree + entered.term.degree < low)
                    low = thisPol.term.degree + entered.term.degree;

                thisPol = thisPol.next;
            }

            entered = entered.next;
        }

        entered = p.poly;

        Node create = front;
        for (int i = low; i <= high; i++) { 
            create.term.degree = i;
            create.term.coeff = 0;

            create.next = new Node (0, 0, null);
            create = create.next;
        }

        entered = p.poly;

        while (entered != null) {
            thisPol = this.poly; 

            while (thisPol != null) {
                int degree = entered.term.degree + thisPol.term.degree;
                create = front;

                while (create != null) {
                    if (create.term.degree == degree) {
                        create.term.coeff = entered.term.coeff * thisPol.term.coeff;
                    }

                    create = create.next;
                }

                thisPol = thisPol.next;
            }

            entered = entered.next;
        }

        create = front;

        while (create != null) {
            if (create.term.degree == high) {
                create.next = null;
                create = create.next;
            }
            else
                create = create.next;
        }

        retPol.poly = front;

        return retPol;
    }
}

我应该得到的答案是：

32.0x^9 + 16.0x^8 + -16.0x^7 + -20.0x^6 + 52.0x^5 + 38.0x^4 + -6.0x^3 + -6.0x^2 + 9.0x + 27.0

但我实际上得到了：

32.0x^9 + 16.0x^8 + -16.0x^7 + -8.0x^6 + 16.0x^5 + 24.0x^4 + 12.0x^3 + -6.0x^2 + -9.0x + 27.0

似乎第3到第6度逻辑是不正确的。我知道这是一个逻辑错误。我只是不确定如何解决问题。我也知道应该为那些不正确的度数添加哪些术语，但它只是看起来它绕过了那个而只显示了一个。

任何提示都将不胜感激。感谢。

Answer 1

我认为你应该总结所有对，而不是在这里选择最后一个（或随机）对：

                if (create.term.degree == degree) {
                    create.term.coeff += entered.term.coeff * thisPol.term.coeff;
                }

[更新]我的修正代码非常适合我：

public class PolynomialTest {
    public static void main(String[] args) {
        // 4x^5 - 2x^3 + 2x + 3
        Polynomial p1 = new Polynomial(new Node(4.0, 5, new Node(-2.0, 3, new Node(2.0, 1, new Node(3.0, 0, null)))));
        // 8x^4 + 4x^3 - 3x + 9
        Polynomial p2 = new Polynomial(new Node(8.0, 4, new Node(4.0, 3, new Node(-3.0, 1, new Node(9.0, 0, null)))));
        Polynomial p3 = p1.multiply(p2);
        System.out.println(p3.toString());
    }
}

class Term {
    int degree;
    double coeff;
}

class Node {
    Term term;
    Node next;
    public Node(double coeff, int degree, Node next) {
        this.term = new Term();
        this.term.degree = degree;
        this.term.coeff = coeff;
        this.next = next;
    }
}

class Polynomial {
    private Node poly;

    public Polynomial() {}

    public Polynomial(Node poly) {
        this.poly = poly;
    }

    public Polynomial multiply(Polynomial p) {
        if (p.poly == null || this.poly == null) {
            Polynomial zero = new Polynomial();
            zero.poly = new Node (0, 0, null);
            return zero;
        } else {

            Polynomial retPol = new Polynomial();
            retPol.poly = new Node(0, 0, null);

            Node front = retPol.poly;
            Node entered = p.poly;
            Node thisPol = this.poly;

            int high = Integer.MIN_VALUE;
            int low = Integer.MAX_VALUE;

            while (entered != null) {
                thisPol = this.poly; 

                while (thisPol != null) {
                    if (thisPol.term.degree + entered.term.degree > high)
                        high = thisPol.term.degree + entered.term.degree;
                    if (thisPol.term.degree + entered.term.degree < low)
                        low = thisPol.term.degree + entered.term.degree;

                    thisPol = thisPol.next;
                }

                entered = entered.next;
            }

            entered = p.poly;

            Node create = front;
            for (int i = low; i <= high; i++) { 
                create.term.degree = i;
                create.term.coeff = 0;

                create.next = new Node (0, 0, null);
                create = create.next;
            }

            entered = p.poly;

            while (entered != null) {
                thisPol = this.poly; 

                while (thisPol != null) {
                    int degree = entered.term.degree + thisPol.term.degree;
                    create = front;

                    while (create != null) {
                        if (create.term.degree == degree) {
                            create.term.coeff += entered.term.coeff * thisPol.term.coeff;
                        }

                        create = create.next;
                    }

                    thisPol = thisPol.next;
                }

                entered = entered.next;
            }

            create = front;

            while (create != null) {
                if (create.term.degree == high) {
                    create.next = null;
                    create = create.next;
                }
                else
                    create = create.next;
            }

            retPol.poly = front;

            return retPol;
        }
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        Node n = poly;
        while (n != null) {
            if (sb.length() > 0)
                sb.append(" + ");
            sb.append(n.term.coeff);
            if (n.term.degree > 0)
                sb.append("x");
            if (n.term.degree > 1)
                sb.append("^").append(n.term.degree);
            n = n.next;
        }
        return sb.toString();
    }
}

此代码完全打印出您的预期：

27.0 + 9.0x + -6.0x^2 + -6.0x^3 + 38.0x^4 + 52.0x^5 + -20.0x^6 + -16.0x^7 + 16.0x^8 + 32.0x^9

多项式乘法度数学与链表的不正确

1 个答案: