一元多项式乘法

/**
*@brief 求两个一元多项式P（X）和Q（X）的乘积 P（x) * Q(X)
        For two unary polynomial P (X) and Q (X) = P (X) (X) * Q
*@author Hxm
*@date 2016/3/26
*
*@note 要求：1.通过键盘随机输入两多项式P（X） 和Q（X）的内容
              2.输出结果要有P（X）和Q（X）的以及它们的乘积P（X）*Q（X）
              Requirements: 1. The random input through the keyboard two polynomial P (X) and Q (X)
              2. The output should have P and Q (X) (X) and their product P * Q (X) (X)

*/


#include<stdio.h>
#include<stdlib.h>
#include<windows.h>
#include<malloc.h>

typedef struct polyNode
{
    float coef;
    int expon;
    struct polyNode *next;
}pNode;
void face()
{
    system("color e4");
    printf("-------------------------------------------------------------------\n");
    printf("*********two polynomial add, muilt, plus*******\n");
    printf("------Please chose one operation to start------\n ");
    printf("0.exit\n");
    printf("1.add two polynomial:\n");
    printf("2.sub two polynomial :\n");
    printf("3.multiply two polynomial:\n ");
}

void insertPoly(pNode *head, pNode *input)
{
    pNode *p, *q;
    int flag=0;
    p=head;   //p is the prior link node
    if(p->next==NULL){
        p->next=input;
    }
    else{
        q=p->next;
        while(flag==0){
            if(input->expon<q->expon){
                if(q->next==NULL){
                    q->next=input;
                    flag=1;
                }
                else{
                    p=q;
                    q=p->next;
                }
            }
            else{
                if(input->expon>q->expon){
                    input->next=q;
                    p->next=input;
                    flag=1;
                }
                else{
                    q->coef=q->coef+input->coef;
                    flag=1;
                    free(input);
                    if(q->coef==0){
                        p->next=q->next;
                        free(q);
                    }
                }
            }
        }

    }

}


pNode *creatPoly(char pch)
{
    pNode *head, *input;
    float x;
    int y;
    head=(pNode *)malloc(sizeof(pNode));
    head->next=NULL;
    printf("Please enter polynomial    %c:(style is :coef expon; input 0 0 to end  ) \n",pch);
    scanf("%f %d", &x, &y);
    while(x!=0){
        input=(pNode *)malloc(sizeof(pNode));
        input->coef=x;
        input->expon=y;
        input->next=NULL;
        insertPoly(head, input);
        printf("please enter the next term of polynomial     %c: (input  0 0 to end) \n", pch);
        scanf("%f %d", &x, &y);
    }
    return head;
}

pNode *addPoly(pNode *head, pNode *prior)
{
    pNode *input;
    int flag=0;
    while(flag==0){
        if(prior->next==NULL)
            flag=1;
        else{
            prior=prior->next;
            input=(pNode *)malloc(sizeof(pNode));
            input->coef=prior->coef;
            input->expon=prior->expon;
            input->next=NULL;
            insertPoly(head, input);
        }
    }
    return head;
}


pNode *subPoly(pNode *head, pNode *prior)
{
    pNode *input;
    int flag=0;
    while(flag==0){
        if(prior->next==NULL){
            flag=1;
        }
        else{
            prior=prior->next;
            input=(pNode *)malloc(sizeof(pNode));
            input->coef=0-prior->coef;
            input->expon=prior->expon;
            input->next=NULL;
            insertPoly(head, input);
        }
    }
    return head;
}


pNode *multPoly(pNode *head1, pNode *head2)
{
    pNode *input, *r, *p;
    int flag=0;
    r=(pNode *)malloc(sizeof(pNode));
    r->next=NULL;
    head1=head1->next;
    p=head2;
    while(flag==0){
        if(p->next==NULL){
            p=head2;
            head1=head1->next;
            continue;
        }
        if(head1==NULL){
            flag=1;
            continue;
        }
        p=p->next;
        input=(pNode *)malloc(sizeof(pNode));
        input->coef=p->coef * head1->coef;
        input->expon=p->expon + head1->expon;
        input->next=NULL;
        insertPoly(r,input);
    }
    return r;
}


void displayPoly(pNode *head)
{
    pNode *p;
    int flag=0;
    p=head->next;
    if(head->next==NULL){
        printf("0\n");
        return  ;
    }
    while(flag==0){
        if(p->coef>0 && head->next!=p)
            printf("+");
         if(p->coef==1) ;
         else if(p->coef==-1)
            printf("-");
         else
            printf("%f",p->coef);
         if(p->expon!=0)
            printf("x^%d", p->expon);
         else if((p->coef==1) || (p->coef==-1))
            printf("1");
         if(p->next==NULL)
            flag=1;
         else
            p=p->next;
    }
    printf("\n");
}


int main()
{
  pNode *p  , *q;
  int choice=-1;
  face();
  while(choice!=0){
    scanf("%d", &choice);
    switch(choice)
    {
    case 0:
        break;
    case 1:
        {
            printf("Your choice is: add two polynomial:\n");
            p=creatPoly(‘p‘);      //input polynomial
            printf("P(x)=");
            displayPoly(p);
            q=creatPoly(‘q‘);
            printf("Q(X)=");
            displayPoly(q);
            printf("R(x)=P(x)+Q(x)=");
            p=addPoly(p, q);
            displayPoly(p);
            choice=-1;
            face();
            break;
        }
    case 2:
        {
            printf("your choice is: sub two polynomial:\n");
            p=creatPoly(‘p‘);      //input polynomial
            printf("P(x)=");
            displayPoly(p);
            q=creatPoly(‘q‘);
            printf("Q(X)=");
            displayPoly(q);
            printf("R(x)=P(x)-Q(x)=");
            p=subPoly(p, q);
            displayPoly(p);
            choice=-1;
            face();
            break;
        }
    case 3:
        {
        printf("your choice is: multiply  two polynomial:\n");
            p=creatPoly(‘p‘);      //input polynomial
            printf("P(x)=");
            displayPoly(p);
            q=creatPoly(‘q‘);
            printf("Q(X)=");
            displayPoly(q);
            printf("R(x)=P(x)*Q(x)=");
            p=multPoly(p, q);
            displayPoly(p);
            choice=-1;
            face();
            break;
        }
    default:
        {
            printf("Error input!! please choose again~~~\n");
            face();
            break;
        }
    }
  }
}