Reading data into list nodes

Question

I am supposed to create a linked list with each node having structure:

struct stack{
    char paint;
    int index;
    struct stack *next;
}
typedef struct stack s;

I am Supposed to create linked list with m nodes by reading m inputs such as:

A 7

B 2

C 1

D 4 ....

so I tried using a for loop like this which is failing and also i tried to sequential scanfs like

scanf("%c",&c);

scanf("%d",&b);

I also tried this:

for(i=0;i<m;i++)
{
    scanf("%c %d",&c,&b);
    temp=(s *)malloc(sizeof(s));
    temp->paint=c;
    temp->index=b;
    temp->next=head;
    head=temp;
    temp=NULL;
}

What am I doing wrong? I am actually scared of scanf so I usually use getchar all the time and if possible please explain how scanf works when inputting from terminal or files which have n rows of inputs. And also alternative statement of while((c=getchar())!='\n') using scanf?

Can you clarify *...which is failing...*? Failing in what way? — lurker, Oct 10 '14 at 19:54
You should really check the results of your function calls; in particular make sure `scanf` returns 2 (read 2 fields). And you're not reading the whitespace after each line (add a space to the end of your format string). — Dmitri, Oct 10 '14 at 20:01
@lurker it is going into the for loop and nothing is happening, all i can see is the terminal waiting for input — sarat, Oct 11 '14 at 03:01
@Dmitri There is not whitespace between inputs i just seperated them here so that it looks clean .sorry for the confusion — sarat, Oct 11 '14 at 03:02
@sarat The whitespace I was referring to was the newlines that separate each line from the next. — Dmitri, Oct 11 '14 at 03:46

ani627 · Accepted Answer · 2014-10-10T20:22:43.340

1

Change your scanf from

scanf("%c %d",&c,&b);

to

scanf(" %c %d",&c,&b);
//     ^Add a space before %c

The problem here is scanf is reading \n after you input a character value and an integer value and then pressing enter key.

A space before % will skip white space (also \n) and it will read the next character that is not white space.

edited Oct 10 '14 at 20:22

answered Oct 10 '14 at 20:01

ani627

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Thank you so much @1336087 skipping the white space fixed the problem, i was frantically searching for whats wrong with the code – sarat Oct 11 '14 at 03:18
@sarat: You are welcome :) If your problem is resolved kindly click on the tick mark and accept an answer which was useful for you. – ani627 Oct 11 '14 at 04:21

score 0 · Answer 2 · answered Oct 10 '14 at 20:47

In scanf, %c and %1s are not the same :

%c reads next character, whatever it can be a space, a newline, ...
%1s reads next printable character

In your use case, I think you should use

scanf("%1s %d",&c,&b);

to correctly skip eventual spaces an newline

Reading data into list nodes

2 Answers2