#include <stdio.h>
struct list {
  int pow,coef;
  struct list *next,*pre;
};
typedef struct list node;
typedef node *link;
link last;

link find(link h,int c, int p) {
  link ptr;
  ptr=h;
  do {
    if ((ptr->coef == c) && (ptr->pow == p)) return ptr;
    ptr=ptr->next;
  } while (ptr != NULL);
  return NULL;
}

void print_forward(link head) {
  link pt1;

  printf("the input polynomial ---> f(X)=");
  pt1=head;
  do {
    if (pt1->pow != 0) printf("%2dX%2d",pt1->coef,pt1->pow);
    else printf("%2d",pt1->coef);
    pt1=pt1->next; if (pt1 != NULL) printf("+");
  } while (pt1 != NULL) ;
  printf("\n");
}

void print_backward(link last) {
  link pt1;

  printf("the input polynomial ---> f(X)=");
  pt1=last;
  do {
    if (pt1->pow != 0) printf("%2dX%2d",pt1->coef,pt1->pow);
    else printf("%2d",pt1->coef);
    pt1=pt1->pre; if (pt1 != NULL) printf("+");
  } while (pt1 != NULL) ;
  printf("\n");
}

link create() {
  link pt1,pt2,head;
  int c,p;

  head=NULL;
  while (1) {
    printf("give me coefficient and power ?"); scanf("%d %d",&c,&p);
    if ((c == 0) && (p == 0)) break;
    pt2=(link)malloc(sizeof(node));
    if (head == NULL) { pt1=head=pt2; pt1->pre=NULL; }
    else { pt1->next=pt2; pt2->pre=pt1; pt1=pt2; }
    pt2->coef=c; pt2->pow=p;
  }
  if (head != NULL) { pt2->next=NULL; last=pt2; }
  return head;
}

void conpoly(link h2,link l1) {
  link pt1,pt2;
  int c,p;

  l1->next=h2; h2->pre=l1;
}

void main() {
  link h1,l1,h2,l2;

  printf("give me the first polynomial -->");
  h1=create(); l1=last; print_forward(h1); print_backward(l1);
  h2=create(); l2=last; print_forward(h2); print_backward(l2);
  conpoly(h2,l1); l1=l2; print_forward(h1); print_backward(l2);
}