Printing a reverse linked list

[Nyah Check]

hey guys so far my code works good but when i enter a code and press '\n' the code statements are executed twice....

.//Filename: rllst.c
//This program prints a reverse linked list.
//Author: Nyah check, chairman, INK Corp..
//Licence: Freeware

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

int print_list( struct node);
int insert_list(void);
struct node
{
    int num;
    struct node *next;
}values;

struct node *first = NULL;
struct node *p, *q;

int main(void)
{
    char code;
    int n;

    printf("\nThis program stores variables in  a linked list and prints all of them in reverse order.");
    printf("\nPress '0': QUIT, 'c': CREATE LIST, 'p': PRINT REVERSED LIST.");

    for ( ; ; )
    {
        printf("\nEnter code: ");
        code = getchar();
        getc(stdin);

        switch(code)
        {
            case '0':   printf("\nThanks for using our software.");
                        printf("\n We would like to receive your comments, suggestions to better our products.");
                        printf("\nINK Corp.. 2012.");
                        exit(EXIT_SUCCESS);

            case 'C':
            case 'c':   insert_list();
                        break;

            case 'P':
            case 'p':   print_list(values);
                        break;

            default:    printf("\nInvalid Command.");
                        break;
        }
    }
    return 0;
}

//insert_list(): This function adds variables to a linked list and returns if it was unsuccessful.
int insert_list(void)
{
    int n;
    struct node *new_node;
    new_node =(struct node *)malloc(sizeof(struct node));

    if ( new_node == NULL)
    {
        printf("\nNo memory to add data.");
        exit(EXIT_FAILURE);
    }

    else

        printf("\nEnter number: ");
        scanf("%d", &n);

        new_node->num = n;
        p == first;
        new_node->next = first;
        q = new_node;

    return 0;
}

//print_list(): This function prints all the values in the linked list in reverse order.
//              starting from the last element.
int print_list( struct node)
{
    printf("\nReverse list");
    printf("\n-------------");
    for ( int i = 1; q != p; q = q->next, i++)
        printf("\n%d. %d ",i, q->num);

    return 0;

}

[anduril462]

How does your code work? It doesn't even compile!

$ make list
gcc -Wall -g -std=c99  -lm -lpthread -lcurses -lefence  list.c   -o list
list.c:9: warning: ‘struct node’ declared inside parameter list
list.c:9: warning: its scope is only this definition or declaration, which is probably not what you want
list.c: In function ‘main’:
list.c:46: error: type of formal parameter 1 is incomplete
list.c:23: warning: unused variable ‘n’
list.c: In function ‘insert_list’:
list.c:75: warning: statement with no effect
list.c: At top level:
list.c:84: error: conflicting types for ‘print_list’
list.c:9: note: previous declaration of ‘print_list’ was here
list.c: In function ‘print_list’:
list.c:84: error: parameter name omitted
make: *** 
[list] Error 1

[Salem]

It compiles OK - if you use a C++ compiler.

$ g++ -Wall foo.cpp
foo.cpp: In function ‘int main()’:
foo.cpp:23: warning: unused variable ‘n’
foo.cpp: In function ‘int insert_list()’:
foo.cpp:75: warning: statement has no effect

Where "for ( int i" is supported, along with unnamed parameters, and necessary casting of malloc.

The OP should really start to use the right compiler for the right language. You need to make sure you learn the language, and not just to accept whatever you can get past the compiler.

Plus the line 75 issue.


> but when i enter a code and press '\n' the code statements are executed twice
That would be line 31 picking up the trailing \n left behind by line 72.
scanf() is pretty awful at the best of times, but trying to mix it with other input methods (like getchar) is a disaster area.

Replace your two lines of getchar/getc with
scanf(" %c", &code); // note the leading space

[Nyah Check]

ok i'll d that but what kind of compiler is @anduril462 using i use the codeblocks gcc compiler and my code runs so you better check yours.....

[anduril462]

ok i'll d that but what kind of compiler is @anduril462 using i use the codeblocks gcc compiler and my code runs so you better check yours.....

My compiler is fine (I use gcc too). You posted invalid C code in the C forum. Your code only compiles if you're using a C++ compiler (see the very first line of Salem's reply). You need to post in the appropriate forum next time.

[Salem]

I think the code is right for the forum - it's just Nyah needs to make sure they're using gcc rather than g++ to compile code.

[Nyah Check]

ok i'll check the code but i don't understand why its happening that way with your compiler

[Nyah Check]

my compiler is codeblocks c /c++ compiler...

[laserlight]

Code::Blocks is an IDE, not a compiler. You should be able to configure it to use gcc instead of g++. Also, naming your source files as ".c" may help.

[Nyah Check]

thanks @laserlight do that right away had no idea........

[Nyah Check]

setup my compiler corectly now.... anyway here is my new code.

//new code

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

int print_list( struct node);
int insert_list(void);
struct node
{
    int num;
    struct node *next;
}values;

struct node *first = NULL;
struct node *q;

int main(void)
{
    char code;

    printf("\nThis program stores variables in  a linked list and prints all of them in reverse order.");
    printf("\nPress '0': QUIT, 'c': CREATE LIST, 'p': PRINT REVERSED LIST.");

    for ( ; ; )
    {
        printf("\nEnter code: ");
        code = getchar();
        getc(stdin);

        switch(code)
        {
            case '0':   printf("\nThanks for using our software.");
                        printf("\n We would like to receive your comments, suggestions to better our products.");
                        printf("\nINK Corp.. 2012.");
                        exit(EXIT_SUCCESS);

            case 'C':
            case 'c':   insert_list();
                        break;

            case 'P':
            case 'p':   print_list(values);
                        break;

            default:    printf("\nInvalid Command.");
                        break;
        }
    }
    return 0;
}

//insert_list(): This function adds variables to a linked list and returns if it was unsuccessful.
int insert_list(void)
{
    int n;
    struct node *new_node;
    new_node =(struct node *)malloc(sizeof(struct node));

    if ( new_node == NULL)
    {
        printf("\nNo memory to add data.");
        exit(EXIT_FAILURE);
    }

    else

        printf("\nEnter number: ");
        scanf("%d", &n);

        new_node->num = n;
        new_node->next = first;
        q = new_node;

    return 0;
}

//print_list(): This function prints all the values in the linked list in reverse order.
//              starting from the last element.
int print_list( struct node)
{
    printf("\nReverse list");
    printf("\n-------------");
    for ( int i = 1; q != NULL; q = q->next, i++)
        printf("\n%d. %d ",i, q->num);

    return 0;

}