用链表实现多项式的加法和乘法

#include<iostream>
#include<fstream>
#include<algorithm>
#include<string>
#include<sstream>
using namespace std;


struct Polynomial{
    int Coef;
    int Exponent;
    Polynomial* Next;
};

Polynomial* ReadDataFromFile(Polynomial* Poly, string s);        //Read polynomial data from a file
void PrintPolynomial(Polynomial* Poly);                //Output polynomial to the screen
void WriteToFile(Polynomial* Poly, string s);  //Write polynomial data to a file
int research(Polynomial* Poly, int Ept);
Polynomial* MultPolynomial(Polynomial* Poly1, Polynomial* Poly2, Polynomial* PolyMult);    //Multiply two polynomials
Polynomial* AddPolynomial( Polynomial* Poly1,Polynomial* Poly2);      //Adding two polynomials



Polynomial* Poly1;
Polynomial* Poly2;
Polynomial* PolySum;                                            //The result of adding two polynomials
Polynomial* PolyMult;                                        //The result of multiplying two polynomials

int main() {
    string s1 = "data1.txt";
    string s2 = "data2.txt";
    Poly1 = ReadDataFromFile(Poly1, s1);
    Poly2 = ReadDataFromFile(Poly2, s2);
    cout << "P1(X)=";
    PrintPolynomial(Poly1);    
    cout << "P2(X)=";
    PrintPolynomial(Poly2);

    s1 = "dataSum.txt";
    s2 = "dataMult.txt";
    PolyMult = MultPolynomial(Poly1, Poly2, PolyMult);
    cout << "P2(X)=P1(X)*P2(X)=";
    PrintPolynomial(PolyMult);

    PolySum = AddPolynomial(Poly1, Poly2);
    cout << "F1(X)=P1(X)+P2(X)=";
    PrintPolynomial(PolySum);

    WriteToFile(PolySum, s1);
    WriteToFile(PolyMult, s2);

    system("pause");
}

Polynomial* ReadDataFromFile(Polynomial* Poly, string s) {
    Poly = new Polynomial;
    Poly->Coef = 0;
    Poly->Exponent = 0;
    Poly->Next = NULL;

    ifstream infile(s.c_str());
    int Coef, Ept;

    if (infile.fail()) {
        cerr << "error" << endl;
    }
    Polynomial *q, *p;
    p = Poly;
    while (!infile.eof()) {
        infile >> Coef >> Ept;
        q = new Polynomial;
        q->Coef = Coef;
        q->Exponent = Ept;
        q->Next = NULL;

        p->Next = q;
        p = q;
    }
    infile.close();
    return Poly;
}
void PrintPolynomial(Polynomial* Poly) {
    if (Poly->Next == NULL) {
        cerr << "List is empty";
        abort();
    }
    Polynomial *p;
    p = Poly->Next;
    int Coef, Ept;
    string s = "";
    string tmp;
    while (p) {
        Coef = p->Coef;
        Ept = p->Exponent;

        if (Coef > 0) {
            if (Ept == 0) {
                stringstream ss;
                ss << Coef<<'+';
                ss >> tmp;
                s += tmp;
            }
            else {
                stringstream ss;
                ss << Coef << "X^" << Ept << '+';
                ss >> tmp;
                s += tmp;
            }
        }
        else if (Coef < 0) {
            if (Ept == 0) {
                stringstream ss;
                ss << Coef<<'+';
                ss >> tmp;
                int len = s.length();
                s = s.substr(0, len - 1);
                s += tmp;
            }
            else {
                stringstream ss;
                ss << Coef << "X^" << Ept << '+';
                ss >> tmp;
                int len = s.length();
                s = s.substr(0, len - 1);
                s += tmp;
            }
        }
        
        p = p->Next;
    }
    int len = s.length();
    if (s[len - 1] == '+') {
        cout << s.substr(0, len - 1) << endl;
    }
    else cout << s << endl;
}

void WriteToFile(Polynomial* Poly, string s) {
    Polynomial* p;
    ofstream outfile(s.c_str());
    if (outfile.fail()) {
        abort();
    }
    p = Poly->Next;
    int Coef, Ept;
    while (p) {
        Coef = p->Coef;
        Ept = p->Exponent;
        outfile << Coef << " " << Ept << " ";
        p = p->Next;
    }
    outfile.close();
}

Polynomial* MultPolynomial(Polynomial* Poly1, Polynomial* Poly2, Polynomial* PolyMult) {
    Polynomial *p1, *p2, *front;

    p1 = Poly1->Next;
    p2 = Poly2->Next;
    PolyMult = new Polynomial;

    PolyMult->Next = NULL;
    int Coef1, Ept1;
    int Coef2, Ept2;
    while (p1) {
        Coef1 = p1->Coef;
        Ept1 = p1->Exponent;

        p2 = Poly2->Next;
        while (p2) {
            Coef2 = p2->Coef;
            Ept2 = p2->Exponent;

            int Coef, Ept;

            Coef = Coef1*Coef2;
            Ept = Ept1 + Ept2;

            Polynomial* rsh=PolyMult;
            front = PolyMult->Next;
            if (rsh&&rsh->Exponent != Ept) {
                while (rsh->Next&&rsh->Next->Exponent != Ept) {
                    rsh = rsh->Next;
                }
            }

            if (rsh->Next) {
                //cout << "rsh->Coef  " << rsh->Coef << "rsh->Exponent  " << rsh->Exponent << endl;
                //cout << "Coef    " << Coef << endl; 
                //cout << rsh->Next->Coef << "  " << Coef << endl;
                //cout << Coef1 << " " << Coef2 << endl;
                rsh->Next->Coef += Coef;
                //cout << "rsh->Coef  " << rsh->Next->Coef << "rsh->Exponent  " << rsh->Next->Exponent << endl;
            }
            else {
                Polynomial *q = new Polynomial;
                q->Coef = Coef;
                q->Exponent = Ept;
                q->Next = NULL;
                rsh->Next = q;    

                //cout << "q->Coef  " << q->Coef << "q->Exponent  " << q->Exponent << endl;

            }

            p2 = p2->Next;
        }
        
        p1 = p1->Next;
    }
    //system("pause");
    return PolyMult;
}


Polynomial* AddPolynomial(Polynomial* Poly1, Polynomial* Poly2) {
    Polynomial *PolySum = new Polynomial;
    PolySum->Next = NULL;

    Polynomial *p1, *p2,*q, *front;

    p1 = Poly1->Next;
    Polynomial* p=PolySum;
    while (p1) {
        q = new Polynomial;
        q->Coef = p1->Coef;
        q->Exponent = p1->Exponent;
        q->Next = NULL;

        p->Next = q;
        p = q;
        p1 = p1->Next;
    }


    int Coef2, Ept2;

    p2 = Poly2->Next;
    while (p2) {
        Coef2 = p2->Coef;
        Ept2 = p2->Exponent;

        p1 = PolySum->Next;
        front = PolySum->Next;
        while (p1&&p1->Exponent!=Ept2) {
            front = p1;
            p1 = p1->Next;
        }
        if (p1) {
            p1->Coef += Coef2;
        }
        else {
            q = new Polynomial;
            q->Coef = Coef2;
            q->Exponent = Ept2;
            q->Next = NULL;

            front->Next = q;
            //cout << "Coef2  " << Coef2 << " " << "Ept2  " << Ept2 << endl;
        }    
        p2 = p2->Next;
    }
    
    return PolySum;
}