One-element polynomial multiplication

/*** @brief the product of two unary polynomial P (x) and Q (x) p (x) * Q (x) for two unary polynomial P (x) and q (x) = P (x) (x) * q* @author hxm*@d Ate 2016/3/26** @note requirements: 1. Randomly input two polynomial p (x) and Q (x) through the keyboard 2. The output should have P (x) and Q (x) and their product p (x) *q (x) requireme Nts:1. The random input through the keyboard the polynomial P (x) and Q (x) 2. The output should has P and Q (x) (x) and their product P * Q (x) (x) */#include <stdio.h> #include <stdlib.h> #in    clude<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 ("------chose one operation to start------\ n");    printf ("0.exit\n");    printf ("1.add-polynomial:\n");    printf ("2.sub-polynomial: \ n"); printf ("3.multiply-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-&                    Gt;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-&GT;COEF=P-&GT;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-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-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-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 }    }  }}

The results are as follows:

One-element polynomial multiplication