Question: How to calculate large factorials using linked list (not array) in C language? I can only find C+……

C code

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#include<stdio.h>
#include<stdlib.h>

struct node
{
int data;
struct node *next;
struct node *prev;
};
typedef struct node *nodeptr;
nodeptr good=NULL,good1,good2,result=NULL;
void insert_start(nodeptr *p,int x) //insert node at start
{
nodeptr q;
q=(nodeptr)malloc(sizeof(struct node));
//q=new node();
if(q==NULL)
{
printf(“memory not allocated”);
getch();
//exit(1);
}
q->data=x;
q->next=q->prev=*p;
*p=q;
}
void insert_after(nodeptr p,int x) //insert node after p
{
nodeptr q;
while(p->next!=NULL)
{
p=p->next;
}
q=(nodeptr)malloc(sizeof(struct node));
if(q==NULL)
{
printf(“memory not allocated!!!!! “);
getch();
//exit(1);
}
q->data=x;
q->next=p->next;
q->prev=p;
p->next=q;
}
void free_list(nodeptr *p) //free the whole list
{
nodeptr q;
while((*p)!=NULL)
{
q=*p;
(*p)=(*p)->next;
free(q);
}
*p=NULL;
}
void printr_nodes(nodeptr p) //print data in list
{
nodeptr q;
q=p;
printf(“n”);
if(q==NULL)
printf(“List is empty”);
while(q->next!=NULL)
q=q->next;
while(q!=NULL)
{
printf(“%d”,q->data);
q=q->prev;
}
}
/* copy list copy1 into list copy2 */
void copy5(nodeptr copy1,nodeptr *copy2)
{
int a;
while(copy1!=NULL)
{
a=copy1->data;
if(*copy2==NULL)
insert_start(&(*copy2),a);
else
insert_after((*copy2),a);
copy1=copy1->next;
}
}
/* add 3lists coming from multiply function */
void add(nodeptr list1,nodeptr list2,nodeptr list3)
{
int value,var,var1,var2,var3,temp=0;
while(list3!=NULL||list1!=NULL||list2!=NULL)
{
if(list1==NULL)
var1=0;
else
{
var1=list1->data;
list1=list1->next;
}
if(list2==NULL)
var2=0;
else
{
var2=list2->data;
list2=list2->next;
}
if(list3==NULL)
var3=0;
else
{
var3=list3->data;
list3=list3->next;
}
var=var1+var2+var3+temp;
if(var>9)
{
value=var%10;
temp=var/10;
}
else
{
value=var;
temp=0;
}

if(result==NULL)
{
insert_start(&result,value);
}
else
insert_after(result,value);

}
if(temp!=0)
insert_after(result,temp);
}
/* multiply the two lists */
void multiply(nodeptr mul1,nodeptr mul2)
{
int a,b,value,d,temp=0,place=0;
nodeptr mult1;
insert_start(&good1,0);
insert_start(&good2,0);
insert_after(good2,0);
while(mul2!=NULL)
{
mult1=mul1;
temp=0;
a=mul2->data;
//printf(“a is %dn”,a);
while(mult1!=NULL)
{
b=(mult1->data)*a;
b=temp+b;
if(b>9)
{
value=b%10;
temp=b/10;
}
else
{
value=b;
temp=0;
}
//printf(“value of VALUE is %dn”,value);
if(place==0)
{
if(good==NULL)
insert_start(&good,value);
else
insert_after(good ,value);
}
else if(place==1)
{
insert_after(good1,value);
}
else if(place==2)
{
insert_after(good2,value);
}
mult1=mult1->next; //point to next node
}
if(place==0 &&temp!=0)
insert_after(good,temp);
else if(place==1 &&temp!=0)
insert_after(good1,temp);
else if(place==2 &&temp!=0)
insert_after(good2,temp);
mul2=mul2->next;
place++;
}
add(good,good1,good2);
}

void main()
{
nodeptr list=NULL,list1=NULL;
int i ,val,val1,num,div;

printf(“enter no. for factorial to calculatedn”);
scanf(“%d”,&num);
val1=num;
while(num>0)
{
div=num%10;
num=num/10;
if(list==NULL)
insert_start(&list,div);
else
insert_after(list ,div);
}
//printf(“in 1st operand”);
//printr_nodes(list);

/* loop upto n-1 to 1*/
for(i=val1-1;i>1;i–)
{
val=i;
while(val>0)
{
div=val%10;
val=val/10;
if(list1==NULL)
insert_start(&list1,div);
else
insert_after(list1,div);
}
//printf(“nin 2nd operand”);
//printr_nodes(list1);
multiply(list,list1);
free_list(&list1);
free_list(&list);
copy5(result,&list);
free_list(&result);
free_list(&good);
free_list(&good1);
free_list(&good2);
}
printf(“n———-in FINAL LIST is————n”);
printr_nodes(list);

}

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Output