I have written a program to multiply two polynomials in the form of single linked lists. I am unable to print output using this code.
The output I am getting is
1st Number: 5x^2 + 4x^1 + 2x^0
2nd Number: 5x^1 + 5x^0
Multiplied polynomial:
How can I fix that?
My code:
// C++ program for multiplication of two polynomials
// using Linked Lists
#include<bits/stdc++.h>
using namespace std;
// Node structure containing power and coefficient of variable
struct node
{
int coeff;
int exp;
struct node *next;
};
void padd(float, int, node**);
// Function to create new node
void create_node(int x, int y, struct node **temp)
{
struct node *r,*z ;
z = *temp;
if(z == NULL)
{
r =(struct node*)malloc(sizeof(struct node));
r->coeff = x;
r->exp = y;
*temp = r;
r->next = (struct node*)malloc(sizeof(struct node));
r = r->next;
r->next = NULL;
}
else
{
r->coeff = x;
r->exp = y;
r->next = (struct node*)malloc(sizeof(struct node));
r = r->next;
r->next = NULL;
}
}
// Function Multiplying two polynomial numbers
void polymul ( struct node *poly1, struct node *poly2,
struct node *poly )
{
struct node *y1 ;
float coeff1;
int exp1 ;
y1 = poly2 ; /* point to the starting of the second linked list */
if ( poly1 == NULL && poly2 == NULL )
return ;
/* if one of the list is empty */
if ( poly1 == NULL )
poly = poly2 ;
else
{
if ( poly2 == NULL )
poly = poly1 ;
else/* if both linked lists exist */
{
/* for each term of the first list */
while ( poly1 != NULL )
{
/* multiply each term of the second linked list with a
term of the first linked list */
while ( poly2 != NULL )
{
coeff1 = poly1 -> coeff * poly2 -> coeff ;
exp1 = poly1 -> exp + poly2 -> exp ;
poly2 = poly2 -> next ;
/* add the new term to the resultant polynomial */
padd ( coeff1, exp1, &poly ) ;
}
poly2 = y1 ; /* reposition the pointer to the starting of
the second linked list */
poly1 = poly1 -> next ; /* go to the next node */
}
}
}
}
/* adds a term to the polynomial in the descending order of the exponent */
void padd ( float coeff, int exp, struct node **s )
{
struct node *r, *temp = *s ;
/* if list is empty or if the node is to be inserted before the first node */
if ( *s == NULL || exp > ( *s ) -> exp )
{
*s=r = (struct node*) malloc ( sizeof ( struct node ) ) ;
(*s) -> coeff = coeff ;
(*s) -> exp = exp ;
(*s)-> next = temp ;
}
else
{
/* traverse the entire linked list to search the position to insert a new node */
while ( temp != NULL )
{
if ( temp -> exp == exp )
{
temp -> coeff += coeff ;
return ;
}
if ( temp -> exp > exp && ( temp -> next -> exp < exp || temp -> next == NULL ) )
{
r = (struct node* )malloc ( sizeof ( struct node ) ) ;
r -> coeff = coeff;
r -> exp = exp ;
r -> next = temp -> next ;
temp -> next = r ;
return ;
}
temp = temp -> next ; /* go to next node */
}
r -> next = NULL ;
temp -> next = r ;
}
}
// Display Linked list
void show(struct node *node)
{
while(node->next != NULL)
{
printf("%dx^%d", node->coeff, node->exp);
node = node->next;
if(node->next != NULL)
printf(" + ");
}
}
// Driver program
int main()
{
struct node *poly1 = NULL, *poly2 = NULL, *poly = NULL;
// Create first list of 5x^2 + 4x^1 + 2x^0
create_node(5,2,&poly1);
create_node(4,1,&poly1);
create_node(2,0,&poly1);
// Create second list of 5x^1 + 5x^0
create_node(5,1,&poly2);
create_node(5,0,&poly2);
printf("1st Number: ");
show(poly1);
printf("\n2nd Number: ");
show(poly2);
poly = (struct node *)malloc(sizeof(struct node));
// Function multiply two polynomial numbers
polymul(poly1, poly2, poly);
// Display resultant List
printf("\nMultiplied polynomial: ");
show(poly);
return 0;
}
You should declare your function padd()
before function polymul
or you can write a function prototype at the top so that the compiler knows that the function padd
will be encountered after polymul
.
For the second error you should typecast the output of malloc
function to struct node *
as malloc returns void *
type value.
Just add the typcasting to the malloc
functions in your code.
r = (struct node*)malloc ( sizeof ( struct node ) ) ;
There were some pointer issues in the linked list. I have fixed them in the ideone link.
#include<bits/stdc++.h>
using namespace std;
// Node structure containing power and coefficient of variable
struct node
{
int coeff;
int exp;
struct node *next;
};
// Function to create new node
void create_node(int x, int y, struct node **temp)
{
struct node *r, *tmp=NULL ;
if(*temp == NULL) // If the list is NULL then add node at First position
{
r =(struct node*)malloc(sizeof(struct node));
r->coeff = x;
r->exp = y;
r->next = NULL;
*temp = r;
/*r->next = (struct node*)malloc(sizeof(struct node));
r = r->next;
r->next = NULL;*/ //Not needed
}
else
{
tmp = *temp;
while (tmp->next != NULL) {
tmp = tmp -> next; //Travel to the end of linked list
}
r = (struct node*)malloc(sizeof(struct node));
r->coeff = x;
r->exp = y;
r->next = NULL;
tmp->next = r; //Add new node to the list
}
}
// Function Adding two polynomial numbers
/* adds a term to the polynomial in the descending order of the exponent */
void padd ( int coeff, int exp, struct node **s )
{
struct node *r, *temp = *s ;
struct node *tmp = *s;
/* if list is empty or if the node is to be inserted before the first node
*/
if ( temp == NULL || exp > ( temp ) -> exp )
{
r = (struct node*)malloc ( sizeof ( struct node ) ) ;
r -> coeff = coeff ;
r -> exp = exp ;
r -> next = temp ;
temp = r;
*s = r;
}
else
{
/* traverse the entire linked list to search the position to insert
a new node */
while ( temp != NULL )
{
if ( temp -> exp == exp )
{
temp -> coeff += coeff ;
return;
} else if ( temp -> exp > exp && ( temp -> next -> exp < exp ||temp ->next == NULL ) )
{
r = (struct node*)malloc ( sizeof ( struct node ) ) ;
r -> coeff = coeff;
r -> exp = exp ;
r -> next = temp -> next ;
temp -> next = r ;
return;
}
temp = temp -> next ; /* go to next node */
}
r -> next = NULL ;
temp -> next = r ;
}
}
struct node * polymul ( struct node *poly1, struct node *poly2, struct node *poly3)
{
struct node *y1 ;
int coeff1;
int exp1 ;
struct node *poly = poly3;
y1 = poly2 ; /* point to the starting of the second linked list */
if ( poly1 == NULL && poly2 == NULL )
return NULL;
/* if one of the list is empty */
if ( poly1 == NULL ) {
poly = poly2 ;
} else
{
if ( poly2 == NULL )
poly = poly1 ;
else /* if both linked lists exist */
{
/* for each term of the first list */
while ( poly1 != NULL )
{
/* multiply each term of the second linked list with a
term of the first linked list */
while ( poly2 != NULL )
{
coeff1 = poly1 -> coeff * poly2 -> coeff ;
exp1 = poly1 -> exp + poly2 -> exp ;
poly2 = poly2 -> next ;
/* add the new term to the resultant polynomial */
padd( coeff1, exp1, &poly) ;
}
poly2 = y1 ; /* reposition the pointer to the starting of
the second linked list */
poly1 = poly1 -> next ; /* go to the next node */
}
}
}
return poly;
}
// Display Linked list
void show(struct node *node)
{
while(node != NULL) // if we use node->next != NULL while will break at the last node skipping it
{
printf("%dx^%d", node->coeff, node->exp);
if(node->next != NULL)
printf(" + ");
node = node->next;
}
}
// Driver program
int main()
{
struct node *poly1 = NULL, *poly2 = NULL, *poly = NULL;
// Create first list of 5x^2 + 4x^1 + 2x^0
create_node(5,2,&poly1);
create_node(4,1,&poly1);
create_node(2,0,&poly1);
// Create second list of 5x^1 + 5x^0
create_node(5,1,&poly2);
create_node(5,0,&poly2);
printf("1st Number: ");
show(poly1);
printf("\n2nd Number: ");
show(poly2);
poly = (struct node *)malloc(sizeof(struct node));
// Function add two polynomial numbers
poly = polymul(poly1, poly2, poly);
// Display resultant List
printf("\nAdded polynomial: ");
show(poly);
return 0;
}
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