Polynomial multiplication using linked list in c - linked-list

Question

Iam working on a program to perform addition,subtraction,multiplication and differentiation operations on a polynomial using linked list in c.
The other operations are working fine except multiplication one.
here is the code
#include<stdio.h>
#include<malloc.h>
#include<conio.h>
struct link{
int coeff;
int pow;
struct link *next;
};
struct link *poly1=NULL,*poly2=NULL,*poly=NULL;
void create(struct link *node)
{
char ch;
do
{
printf("\n\nenter coeff:");
scanf("%d",&node->coeff);
printf("\nenter power:");
scanf("%d",&node->pow);
node->next=(struct link*)malloc(sizeof(struct link));
node=node->next;
node->next=NULL;
printf("\ncontinue(y/n):");
ch=getch();
}
while(ch=='y' || ch=='Y');
}
void show(struct link *node)
{
while(node->next!=NULL)
{
printf("%dx^%d",node->coeff,node->pow);
node=node->next;
if(node->next!=NULL)
printf(" + ");
}
}
void polyadd(struct link *poly1,struct link *poly2,struct link *poly)
{
while(poly1->next && poly2->next)
{
if(poly1->pow>poly2->pow)
{
poly->pow=poly1->pow;
poly->coeff=poly1->coeff;
poly1=poly1->next;
}
else if(poly1->pow<poly2->pow)
{
poly->pow=poly2->pow;
poly->coeff=poly2->coeff;
poly2=poly2->next;
}
else
{
poly->pow=poly1->pow;
poly->coeff=poly1->coeff+poly2->coeff;
poly1=poly1->next;
poly2=poly2->next;
}
poly->next=(struct link *)malloc(sizeof(struct link));
poly=poly->next;
poly->next=NULL;
}
while(poly1->next || poly2->next)
{
if(poly1->next)
{
poly->pow=poly1->pow;
poly->coeff=poly1->coeff;
poly1=poly1->next;
}
if(poly2->next)
{
poly->pow=poly2->pow;
poly->coeff=poly2->coeff;
poly2=poly2->next;
}
poly->next=(struct link *)malloc(sizeof(struct link));
poly=poly->next;
poly->next=NULL;
}
}
void polysub(struct link *poly1,struct link *poly2,struct link *poly)
{
while(poly1->next && poly2->next)
{
if(poly1->pow>poly2->pow)
{
poly->pow=poly1->pow;
poly->coeff=poly1->coeff;
poly1=poly1->next;
}
else if(poly1->pow<poly2->pow)
{
poly->pow=poly2->pow;
poly->coeff=poly2->coeff;
poly2=poly2->next;
}
else
{
poly->pow=poly1->pow;
poly->coeff=poly1->coeff-poly2->coeff;
poly1=poly1->next;
poly2=poly2->next;
}
poly->next=(struct link *)malloc(sizeof(struct link));
poly=poly->next;
poly->next=NULL;
}
while(poly1->next || poly2->next)
{
if(poly1->next)
{
poly->pow=poly1->pow;
poly->coeff=poly1->coeff;
poly1=poly1->next;
}
if(poly2->next)
{
poly->pow=poly2->pow;
poly->coeff=poly2->coeff;
poly2=poly2->next;
}
poly->next=(struct link *)malloc(sizeof(struct link));
poly=poly->next;
poly->next=NULL;
}
}
void polymul(struct link *n1, struct link *n2, struct link *n)
{
struct link * n2beg=n2;
while (n1)
{
struct link * temp=(struct link *)malloc(sizeof(struct link));
temp->next=NULL;
n2=n2beg;
while (n2)
{
temp->coeff = n1->coeff * n2->coeff;
temp->pow = n1->pow + n2->pow;
n2 = n2->next;
temp->next=(struct link *)malloc(sizeof(struct link));
temp=temp->next;
temp->next=NULL;
}
polyadd(temp,n,n);
n1 = n1->next;
free(temp);
}
}
void diff(struct link* p1,struct link* p2)
{
while(p1->next!=NULL)
{
p2->coeff=p1->coeff*p1->pow;
p2->pow=p1->pow-1;
p2->next=NULL;
p2->next=(struct link *)malloc(sizeof(struct link));
p2=p2->next;
p2->next=NULL;
p1=p1->next;
}
}
main()
{
int op;
char ch;
do{
poly1=(struct link *)malloc(sizeof(struct link));
poly2=(struct link *)malloc(sizeof(struct link));
poly=(struct link *)malloc(sizeof(struct link));
printf("\n\nWhat do you want to do?\n1.Addition\n2.Subtraction
\n3.Multiplication\n4.Differentiation\n0.Exit
\nEnter your choice:");
scanf("%d",&op);
switch(op)
{
case 1:
printf("\n\nenter 1st polynomial:");
create(poly1);
printf("\n\nenter 2nd polynomial:");
create(poly2);
printf("\n1st Polynomial:\t");
show(poly1);
printf("\n2nd Polynomial:\t");
show(poly2);
polyadd(poly1,poly2,poly);
printf("\nAdded polynomial:\t");
show(poly);
break;
case 2:
printf("\n\nenter 1st polynomial:\t");
create(poly1);
printf("\n\nenter 2nd polynomial:\t");
create(poly2);
printf("\n\n1st Polynomial:\t");
show(poly1);
printf("\n\n2nd Polynomial:\t");
show(poly2);
polysub(poly1,poly2,poly);
printf("\n\nSubtracted polynomial:\t");
show(poly);
break;
case 3:
printf("\n\nenter 1st polynomial:");
create(poly1);
printf("\n\nenter 2nd polynomial:");
create(poly2);
printf("\n\n1st Polynomial:\t");
show(poly1);
printf("\n\n2nd Polynomial:\t");
show(poly2);
polymul(poly1,poly2,poly);
printf("\n\nMultiplied polynomial:\t");
show(poly);
break;
case 4:
printf("\n\nenter polynomial:");
create(poly1);
printf("\n\nPolynomial:\t");
show(poly1);
diff(poly1,poly2);
printf("\n\nDifferentiated Polynomial:\t");
show(poly2);
break;
}
/* printf("\n Want to continue? Y/N:");
ch=getch();*/
}
while(op);
}

Answer 1

polyadd(temp,n,n) as used in polymul() has trouble coping with using n as a source polynomial and as the sum destination polynomial.
Either re-work polyadd() to cope with parameters that point to the same polynomial or re-work the call of polyadd() in polymul() to use distinct polynomials. Suggest the first.

Answer 2

I did not go through your full code, as I found an error in your create() function. Note that you have passed poly1 to the function create() as argument.
This not correct as C follows call by value. What happens is only the value of poly1 (which is still un-initialised) is passed and *node stores that value. It's better to pass the address of poly1 as argument and catch that value in the function using pointer to pointer.

Answer 3

#include<stdio.h>
#include <conio.h>
struct node
{
int c,e;
struct node *link;
}*start1=NULL,*start2=NULL,*start3=NULL,*temp1,*temp2,*temp3,*new_node;
int delete_dup(int h)
{
struct node *cr,*prev,*run,*tmp;
cr = start3->link;
prev = start3;
while(cr != NULL){
run = start3;
while(run != cr)
{
if(run->e == cr->e)
{
run->c+=cr->c;
tmp = cr;
cr = cr->link;
prev->link = cr;
remove(tmp);h--;
break;
}
run = run->link;
}
if(run == cr){
cr = cr->link;
prev = prev->link;
}
}
return h;
}
void main()
{
int n,m,i,j,k;
puts("Enter the number of terms in first polynomial");
scanf("%d",&n);
for(i=0;i<n;i++)
{
new_node=(struct node*)malloc(sizeof(struct node));
new_node->link=NULL;
puts("C=");
scanf("%d",&new_node->c);
puts("E=");
scanf("%d",&new_node->e);
new_node->link=start1;
start1=new_node;
}
puts("Enter the number of terms in first polynomial");
scanf("%d",&m);
for(i=0;i<m;i++)
{
new_node=(struct node*)malloc(sizeof(struct node));
new_node->link=NULL;
puts("C=");
scanf("%d",&new_node->c);
puts("E=");
scanf("%d",&new_node->e);
new_node->link=start2;
start2=new_node;
}
temp1=start1;
temp2=start2;
i=0; j=0;
while(i<m)
{
j=0; temp1=start1;
while(j<n)
{
new_node=(struct node*)malloc(sizeof(struct node));
new_node->link=NULL;
new_node->c=temp1->c*temp2->c;
new_node->e=temp1->e+temp2->e;
new_node->link=start3;
start3=new_node;
j++;
temp1=temp1->link;
}
temp2=temp2->link;
i++;
}
i=0;
k=delete_dup(m*n);
temp3=start3;
while(i<k-1)
{
printf("(%dx^%d)+",temp3->c,temp3->e);
temp3=temp3->link;
i++;
}
printf("(%dx^%d)",temp3->c,temp3->e);
}

Answer 4

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
struct node{
int coef,pow;
struct node *next;
};
struct node* create()
{
int c;
struct node *new_node=NULL;
struct node *head=NULL,*temp;
do{
new_node=(struct node*)malloc(sizeof(struct node));
printf("\nEnter coef :");
scanf("%d",&new_node->coef);
printf("\nEnter power : ");
scanf("%d",&new_node->pow);
if(head==NULL)
{
head=new_node;
head->next=NULL;
temp=new_node;
}
else
{
temp->next=new_node;
temp=temp->next;
temp->next=NULL;
}
printf("\nDo you want to continue :");
scanf("%d",&c);
}while(c==1);
return head;
}
void print(struct node *p)
{
while(p!=NULL)
{
printf("|%d|%d|->",p->coef,p->pow);
p=p->next;
}
}
struct node* create_new(int p, int q)
{
struct node *nn=(struct node*)malloc(sizeof(struct node));
nn->coef=p;
nn->pow=q;
nn->next=NULL;
return nn;
}
struct node* add(struct node *poly1,struct node *poly2)
{
struct node *tempadd,*temp;
struct node *temp1=poly1;
struct node *temp2=poly2,*head=NULL;
while(temp1!=NULL && temp2!=NULL)
{
if(temp1->pow==temp2->pow)
{
tempadd=create_new(temp1->coef+temp2->coef,temp2->pow);
temp1=temp1->next;
temp2=temp2->next;
}
else if(temp1->pow<temp2->pow)
{
tempadd=create_new(temp2->coef,temp2->pow);
temp2=temp2->next;
}
else
{
tempadd=create_new(temp1->coef,temp1->pow);
temp1=temp1->next;
}
if(head==NULL)
{
head=tempadd;
temp=head;
}
else
{
temp->next=tempadd;
temp=temp->next;
}
}
if(temp1!=NULL)
{
while(temp1!=NULL)
{
tempadd=create_new(temp1->coef,temp1->pow);
temp1=temp1->next;
temp->next=tempadd;
temp=temp->next;
}
}
else if(temp2!=NULL)
{
while(temp2!=NULL)
{
tempadd=create_new(temp2->coef,temp2->pow);
temp2=temp2->next;
temp->next=tempadd;
temp=temp->next;
}
}
return head;
}
void main()
{
struct node *head1,*head2,*head3;
head1=create();
print(head1);
head2=create();
print(head1);
printf("\n");
print(head2);
printf("\n");
head3=add(head1,head2);
printf("\n\nResult : ");
print(head3);
getch();
}

Answer 5

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
typedef struct node {
struct node *previous;
int coef;
int pow;
struct node *next;
}poly;
poly *locate(int,poly *);
void display(poly *);
poly *mult(poly *,poly *,poly *);
void display2(poly *);
void main()
{
char ch;
poly *s1,*s2,*s3,*head1,*head2,*head3,*s4;;
s1=(poly *)malloc(sizeof(poly));
s1->previous=NULL;
head1=s1;
s2=(poly *)malloc(sizeof(poly));
s2->previous=NULL;
head2=s2;
head3=s3;
printf("Enter first polynomial :\n");
do{ //Input for polynomial-1
printf("Enter co-efficient : ");
scanf("%d",&s1->coef);
printf("Enter exponent : ");
scanf("%d",&s1->pow);
printf("Do you want to enter more terms(Y/N) : ");
scanf(" %c",&ch);
if(ch=='Y'){
s1->next=(poly*)malloc(sizeof(poly));
s1->next->previous=s1;
s1=s1->next;
}
else {
s1->next=NULL;
break;
}
}while(1);
printf("Enter second polynomial : \n");
do{ //input for polynomial-2
printf("Enter co-efficient : ");
scanf("%d",&s2->coef);
printf("Enter exponent : ");
scanf("%d",&s2->pow);
printf("Do you want to enter more terms(Y/N) : ");
scanf(" %c",&ch);
if(ch=='Y'){
s2->next=(poly*)malloc(sizeof(poly));
s2->next->previous=s2;
s2=s2->next;
}
else {
s2->next=NULL;
break;
}
}while(1);
printf("Entered polynomials are : \n");
display(s1);
printf("\n");
display(s2);
s3=NULL;
s4=mult(s1,s2,s3);
printf("Resultant Polynomial after multiplication :\n");
display(s4);
}
void display(poly *a)
{
while(a!=NULL)
{
printf("%dx^%d",a->coef,a->pow);
if(a->previous!=NULL)
printf(" + ");
a=a->previous;
}
}
poly *mult(poly *s1,poly *s2,poly *s3)
{
while(s1->previous!=NULL)
s1=s1->previous;
while(s2->previous!=NULL)
s2=s2->previous;
while(s1)
{
while(s2->previous!=NULL)
s2=s2->previous;
while(1)
{
if(s2->next!=NULL)
{
poly *s4;
if(s3==NULL)
{
s3=(poly *)malloc(sizeof(poly));
s3->pow=s1->pow+s2->pow;
s3->coef=s1->coef*s2->coef;
s3->previous==NULL;
s3->next==NULL;
}
else
{
s4=locate(s1->pow+s2->pow,s3);
if(s4==NULL)
{
s3->next=(poly *)malloc(sizeof(poly));
s3->next->previous=s3;
s3=s3->next;
s3->pow=s1->pow+s2->pow;
s3->coef=s1->coef*s2->coef;
s3->next==NULL;
}
else
{
s4->coef=(s4->coef)+(s1->coef*s2->coef);
}
}
s2=s2->next;
}
else
{
poly *s4;
if(s3==NULL)
{
s3=(poly *)malloc(sizeof(poly));
s3->pow=s1->pow+s2->pow;
s3->coef=s1->coef*s2->coef;
s3->previous==NULL;
s3->next==NULL;
}
else{
s4=locate(s1->pow+s2->pow,s3);
if(s4==NULL)
{
s3->next=(poly *)malloc(sizeof(poly));
s3->next->previous=s3;
s3=s3->next;
s3->pow=s1->pow+s2->pow;
s3->coef=s1->coef*s2->coef;
s3->next==NULL;
}
else
{
s4->coef=s4->coef+s1->coef*s2->coef;
}
}
break;
};
}s1=s1->next;
}return s3;
}
poly *locate(int exp,poly *s3)
{
if(s3==NULL)
{
return NULL;
}
else if(s3->pow==exp)
{
return s3;
}
else{
return locate(exp,s3->previous);
}
}
I considered the first term of first polynomial and multiplied with all the terms of second polynomial thereby creating a primary linked list of multiplied polynomial. As next piece of code I considered next term of first polynomial and then multiplied and searched in the multiplied polynomial for the same index and added the result to it, If it is not present I created a new node in the multiplied polynomial.
Happy Coding