C program to add two polynomials using linked list.

#include<stdio.h>
#include<malloc.h>
struct node
{
float coef;
int expo;
struct node *link;
};
typedef struct node *NODE;
NODE insert(NODE start,float co,int ex)
{
NODE ptr,tmp;
tmp= (NODE)malloc(sizeof(struct node));
tmp->coef=co;
tmp->expo=ex;
if(start==NULL || ex>start->expo)
{
tmp->link=start;//setting the start
start=tmp;
}
else
{
ptr=start;
while(ptr->link!=NULL && ptr->link->expo>ex)
ptr=ptr->link;
tmp->link=ptr->link;
ptr->link=tmp;
if(ptr->link==NULL)
tmp->link=NULL;
}
return start;
}
NODE poly_add(NODE p1,NODE p2)
{
NODE p3_start,p3,tmp;
p3_start=NULL;
if(p1==NULL && p2==NULL)
return p3_start;
while(p1!=NULL && p2!=NULL )
{
tmp=(NODE)malloc(sizeof(struct node));
if(p3_start==NULL)
{
p3_start=tmp;
p3=p3_start;
}
else
{
p3->link=tmp;
p3=p3->link;
}
if(p1->expo > p2->expo)
{
tmp->coef=p1->coef;
tmp->expo=p1->expo;
p1=p1->link;
}
else
if(p2->expo > p1->expo)
{
tmp->coef=p2->coef;
tmp->expo=p2->expo;
p2=p2->link;
}
else
if(p1->expo == p2->expo)
{
tmp->coef=p1->coef + p2->coef;
tmp->expo=p1->expo;
p1=p1->link;
p2=p2->link;
}
}
while(p1!=NULL)
{
tmp=(NODE)malloc(sizeof(struct node));
tmp->coef=p1->coef;
tmp->expo=p1->expo;
if (p3_start==NULL)
{
p3_start=tmp;
p3=p3_start;
}
else
{
p3->link=tmp;
p3=p3->link;}
p1=p1->link;
}
while(p2!=NULL)
{
tmp=(NODE)malloc(sizeof(struct node));
tmp->coef=p2->coef;
tmp->expo=p2->expo;
if (p3_start==NULL)
{
p3_start=tmp;
p3=p3_start;}
else
{
p3->link=tmp;
p3=p3->link;
}
p2=p2->link;
}/*End of while*/
p3->link=NULL;
return p3_start;
}
NODE enter(NODE start)
{
int i,n,ex;
float co;
printf("\nHow many terms u want to enter:");
scanf("%d",&n);
for(i=1;i<=n;i++)
{
printf("\nEnter coeficient for term %d:",i);
scanf("%f",&co);
printf("Enter exponent for term %d:",i);
scanf("%d",&ex);
start=insert(start,co,ex);
}
return start;
}
void display(NODE ptr)
{
if (ptr==NULL)
   printf ("\nEmpty\n");
   return;
while(ptr!=NULL)
{
printf ("(%.1fx^%d) + ", ptr->coef,ptr->expo);
ptr=ptr->link;
}
printf ("\b\b \n"); /* \b\b to erase the last + sign*/
}
void main()
{
NODE p1_start,p2_start,p3_start;
p1_start=NULL;
p2_start=NULL;
p3_start=NULL;
printf("\nPolynomial 1 :\n");
p1_start=enter(p1_start);
printf("\nPolynomial 2 :\n");
p2_start=enter(p2_start);
p3_start=poly_add(p1_start,p2_start);
printf("\nPolynomial 1 is: ");
display(p1_start);
printf ("\nPolynomial 2 is: ");
display(p2_start);
printf ("\nAdded polynomial is: ");
display(p3_start);
getch();
}