Storing a number as digits in a linked list

[Raghav Gupta]

Homework Statement

Create a class named digit, which stores a node holding a digit. Include appropriate data

members and member functions to do the following: (a) Read a long number (datatype is double)

from user and store each digit of the long number as a node value. For example, if the input number

is 8475483 then list is 8->4->7->5->4->8->3. (b) Delete alternate digits, get back the number and

display. For example for the list in (a) the result of delete alternate digits is 8->7->4->3 and

display.

Homework Equations

NA

The Attempt at a Solution

I am not able to extract digits as % is not valid for double datatype. Otherwise the program runs fine when I change the datatype to int and value is in range of int.

#include<iostream.h>
#include<conio.h>

class Digit{
    int data;
    Digit*next,*head;
    public:
    Digit()
    {
    head=NULL;
    }
    void read();
    void delAlt();
    void display();
      };

    void Digit::read(){
    Digit*node=new Digit;
    int num;
    cout<<"Enter number:" ;
    cin>>num;
    node->data=num%10;
    node->next=NULL;
    head=node;
    num=num/10;
    while(num>0){
    node=new Digit;
    node->data=num%10;
    node->next=head;
    head=node;
    num=num/10;}}

    void Digit:: delAlt(){
    Digit*temp,*temp1;
    temp1=head;
    while(temp1!=NULL){
    temp=temp1->next;
    temp1->next=temp->next;
    delete temp;
    temp1=temp1->next;}}

    void Digit::display(){
    Digit*temp=head;
    while(temp!=NULL){
    cout<<temp->data;
    temp=temp->next;}}

    void main(){
    clrscr();
    Digit d;
    d.read();
    d.delAlt();
    d.display();
    getch();
         }

 

[rcgldr]

You should be able to use fmod() for doubles. Include < math.h > . Are you supposed to handle numbers with fractional components such as 123.456 or negative numbers?

 

[Raghav Gupta]

You should be able to use fmod() for doubles.

I used fmod() but then the output is not coming as required.
Output is like this
000000000
000000874 something like that.

 

[rcgldr]

After using fmod(), convert the remainder to an integer.

 

[Raghav Gupta]

After using fmod(), convert the remainder to an integer.

I modified the code to,
double num;
and node->data=(int) fmod(num, 10) ;
but the output is leading with 0. the end digits are fine in this output:
00000000
000008743

 

[rcgldr]

Why is the code calling d.delAlt() before doing d.display()?

 

[Raghav Gupta]

Why is the code calling d.delAlt() before doing d.display()?

Because it is not asked in question to display before deleting alternate nodes.
If I input number as 8475483, and display before delAlt and also after delAlt, then output is like this
0000000000
0000000000
0084754830
0000000000
0087430000

 

[rcgldr]

Follow up, while (num > 0) isn't going to work for doubles, as you'll have a fraction part after each divide. The following should work to fix this (assuming user enters integer type numbers), you'll need to make this change in two places:

        // ...
        num -= node->data;   // subtract the low order digit from num
        num /= 10.;          // divide num by 10.

Also delAlt() has a problem if an odd number of digits is entered.

 

[Raghav Gupta]

Follow up, while (num > 0) isn't going to work for doubles, as you'll have a fraction part after each divide. The following should work to fix this (assuming user enters integer type numbers), you'll need to make this change in two places:

        // ...
        num -= node->data;   // subtract the low order digit from num
        num /= 10.;          // divide num by 10.

Also delAlt() has a problem if an odd number of digits is entered.

Thanks it is working fine now. delAlt() is working fine for me even when there are odd number of digits.
For eg:
input number: 8475483 (odd number of digits)
Output: 8475483 (number as separate digits in link list)
8743 ( deleting alternate nodes)

 

[rcgldr]

Here is an alternate way of doing the divide part:

	num = floor(num/10.);

delAlt() may be working for odd number of digits, but I'm getting an invalid memory access. I added a check to avoid looking for NULL->next:

void Digit::delAlt(){
    Digit*temp,*temp1;
    temp1=head;
    while(temp1 != NULL){
        temp=temp1->next;
        if(temp == NULL){
			break;}
        temp1->next=temp->next;
        delete temp;
        temp1=temp1->next;}
}

 

[Raghav Gupta]

Here is an alternate way of doing the divide part:

    num = floor(num/10.);

Thanks, I understand the floor function aka greatest integer function.

delAlt() may be working for odd number of digits, but I'm getting an invalid memory access. I added a check to avoid looking for NULL->next:

In Turbo c++ it was not giving a warning or error. I think it takes NULL->next as NULL in turbo c++