Addition of positive numbers using linked list: C code

Addition of large positive integers in C is quite difficult since there will be overflow error once the range of 'int' is crossed. But this problem can be overcome by the use of linked list. Happy addition! 



#include<stdio.h>
#include<stdlib.h>
struct numberList {
    int data;
    struct numberList *nextDigit;
    struct numberList *revDigit;
    };
    typedef struct numberList node;
void inputNumber(node*);
void display(node*,int);   
void addNumber(node*,node*);
int main() {
   
    node *firstNumber,*secondNumber,*sum;
    firstNumber = (node *)malloc(sizeof(node));
    secondNumber = (node *)malloc(sizeof(node));
    printf("\n Enter the first number(one digit at a time) type -1 to terminate the number:");
    printf("\n Enter the digit:");
    scanf("%d",&firstNumber->data);
    inputNumber(firstNumber);
   
    printf("\n Enter the second number(one digit at a time) type -1 to terminate the number:");
    printf("\n Enter the digit:");
    scanf("%d",&secondNumber->data);
    inputNumber(secondNumber);
   
    display(firstNumber,1);
    display(secondNumber,2);
   
    addNumber(firstNumber,secondNumber);   
    return 0;
    }   
void addNumber(node *p,node *q) {
    int len1=0,len2=0,min,i,once=0;
    while (p->nextDigit !=NULL) {
        len1++;
        p = p->nextDigit;
        }
    p = p->revDigit;   
    while (q->nextDigit !=NULL) {
        len2++;
        q = q->nextDigit;
        }
    q = q->revDigit;
    min = len1 <= len2 ? len1:len2;
    node *sum,*tmp,*sum1;   
    sum = (node *)malloc(sizeof(node));
    sum1 = sum;
    sum->revDigit = NULL;
    for ( i = 1; i <= min; i++) {
        sum->data = (p->data+q->data+once)%10;
        tmp = sum;
        once = (p->data+q->data+once)/10;
        p=p->revDigit;
        q=q->revDigit;
        sum->nextDigit = (node *)malloc(sizeof(node));
        sum = sum->nextDigit;
        sum->revDigit=tmp;
        }
    if ( len1 == len2 && once !=0) {
        sum->data = once;
        sum->revDigit=tmp;
        }   
    if (len1 > len2) {
        int t = len1-len2;
        sum = sum->revDigit;
        for ( i = 1; i<=t; i++) {
            tmp = sum;
            sum->nextDigit = (node *)malloc(sizeof(node));
            sum = sum->nextDigit;
            sum->revDigit=tmp;
            sum->data = (p->data+once)%10;
            once = (p->data+once)/10;
            p = p->revDigit;
            } 
        if ( once !=0) {
            tmp = sum;
            sum->nextDigit = (node *)malloc(sizeof(node));
            sum = sum->nextDigit;
            sum->data = once;
            sum->revDigit=tmp;
            }
               
        }   
    if (len1 < len2) {
        sum = sum->revDigit;
        int t = len2-len1;
        for ( i = 1; i<=t; i++) {
            tmp = sum;
            sum->nextDigit = (node *)malloc(sizeof(node));
            sum = sum->nextDigit;
            sum->revDigit=tmp;
            sum->data = (q->data+once)%10;
            once = (q->data+once)/10;
            q = q->revDigit;
            }
        if ( once !=0) {
            tmp = sum;
            sum->nextDigit = (node *)malloc(sizeof(node));
            sum = sum->nextDigit;
            sum->data = once;
            sum->revDigit=tmp;
            }   
        }   
    sum->nextDigit = NULL;   
    printf("\n Sum of the numbers is:");
    while (sum1->nextDigit !=NULL) {
        //printf("\n%d",sum1->data);
        sum1 = sum1->nextDigit;
        }
    //sum1 = sum1->revDigit;   
    while (sum1 !=NULL) {
        printf("%d",sum1->data);
        sum1 = sum1->revDigit;
        }
    printf("\n");   
    }   
void display(node *p,int tx) {
    if (tx==1)
        printf("\nFirst Number\n");
    else
        printf("\nSecond Number\n");
    while (p->nextDigit !=NULL) {
        printf("%d",p->data);
        p = p->nextDigit;
        }
    p = p->revDigit;   
    /*while (p !=NULL) {
        //printf("%d",p->data);
        p = p->revDigit;
        }*/   
    }   
void inputNumber(node *p) {
    node *q;
    p->revDigit = NULL;
    while (1) {
        q = p;
        p->nextDigit = (node *)malloc(sizeof(node));
        p = p->nextDigit;
        printf("\n Enter the digit:");
        scanf("%d",&p->data);
        p->revDigit = q;
        if (p->data == -1)
            break;
        }
    p->nextDigit = NULL;
    }     

C Program #9

/*Doubly Linked List */

#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
struct list_element
{
int d;
struct list_element *next,*prev;
};
typedef list_element node;
void create(node *);
void displayn(node *);
void displayr(node *);
node *search(node *);
node *inserteb(node *);
void insertel(node *);
void inserte(node *);
node *deletef(node *);
void deletee(node *);
void deleteb(node *);
int main()
{
int choice;
node *root,*record,*tag ;
record=(node *)malloc(sizeof(node));
root=record;
printf("\n ***********************MENU FOR LIST******************* \n");
printf("\n Press 1 to create:");
printf("\n Press 2 to display list in forward drection:");
printf("\n Press 3 to display list in reverse direction:");
printf("\n Press 4 to search in the list:");
printf("\n Press 5 to inserte at the begining of the list:");
printf("\n Press 6 to inserte at the end of the list:");
printf("\n Press 7 to inserte between first and last element:");
printf("\n Press 8 to delete the first element:");
printf("\n Press 9 to delete the last elemnt:");
printf("\n Press 10 to delete between the last and first elements:");
printf("\n Press 11 to exit:");
while(1)
{
printf("\n Enter your choice:");
scanf("%d",&choice);
switch(choice)
{
case 1:
create(root);
break;
case 2:
displayn(root);
break;
case 3:
displayr(root);
break;
case 4:
tag=search(root);
if(tag==NULL)
printf("\n Element not found:\n");
else
printf("\n The element is %d",tag->d);
break;
case 5:
root=inserteb(root);
break;
case 6:
insertel(root);
break;
case 7:
inserte(root);
break;
case 8:
root=deletef(root);
break;
case 9:
deletee(root);
break;
case 10:
deleteb(root);
   break;
case 11:
exit(0);
break;
default:
break;
}
}
return 0;
}
void create(node *record)
{
int i,n;
node *p;
printf("\n Enter the number of elements:");
scanf("%d",&n);
printf("\n Enter the elements:\n");
scanf("%d",&record->d);
record->prev=NULL;
for(i=1;i<=n-1;i++)
{
p=record;
record->next=(node *)malloc(sizeof(node));
record=record->next;
scanf("%d",&record->d);
record->prev=p;
}
record->next=NULL;
return;
}
void displayn(node *record)
{
 printf("\n");
while(record!=NULL)
{
printf("\t %d",record->d);
record=record->next;
}


}
void displayr(node *record)
{
printf("\n");
while(record->next!=NULL)
{
 // printf("\t %d",record->d);
record=record->next;
}
printf("\n");
while(record!=NULL)
{
printf("\t %d",record->d);
record=record->prev;
}
}
node *search(node *record)
{
int n,flag=0;
node *p;
printf("\n Enter the element to be searched:\n");
scanf("%d",&n);
while(record!=NULL)
{
if(record->d==n)
{
flag=1;
p=record;
break;
}
record=record->next;
}
if(flag==1)
return (p);
else
return (NULL);
}
node *inserteb(node *record)
{
node *p;
p=(node *)malloc(sizeof(node));
printf("\n Enter the element to be inserted:");
scanf("%d",&p->d);
p->next=record;
record->prev=p;
p->prev=NULL;
return (p);
}
void insertel(node *record)
{
node *p;
p=(node *)malloc(sizeof(node));
printf("\n Enter the element to be inserted:");
scanf("%d",&p->d);
while(record->next!=NULL)
{
record=record->next;
}
record->next=p;
p->next=NULL;
p->prev=record;
}
void inserte( node *record)
{
node *p,*tag,*pv;
displayn(record);
printf("\n Enter the element after which insertion has to be done:");
tag=search(record);
if(tag==NULL)
{
printf("\n Cannot be inserted");
}
else
{
pv=tag;
p=(node *)malloc(sizeof(node));
printf("\n Enter the element to be inserted:");
scanf("%d",&p->d);
p->next=tag->next;
tag->next=p;
p->prev=pv;
p->next->prev=p;

}
}
node *deletef(node *record)
{
node *p;
p=record->next;
p->prev=NULL;
free(record);
return(p);
}
void deletee(node *record)
{
 node *p;
while(record->next!=NULL)
{
record=record->next;
}
p=record->prev;
p->next=NULL;
p->prev=record->prev->prev;
   free(record);
}
void deleteb(node *record)
{
 node *p,*tag;
 displayn(record);
 printf("\n Item to be deleted, should be searched:\n");
 tag=search(record);
 if(tag==NULL)
printf("\n Element not found, try again");
 else
{
p=tag->prev;
p->next=tag->next;
p->next->prev=p;
free(tag);
}
}