Program moving values in vectors... need help.

I have written a program that, should move values of a given vector, but id does nothing after declarating for how many places move te values. If you could check the code and write whatis wrong, i would be grateful.

Code:

---

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

int przesun(int t[], int p);

void main()
{
        int k;
        int w[10];
        printf ("Define, how many places you want to move values: ");
        scanf ("%d\n",&k);
        przesun (w,k);
}

int przesun (int t[], int p)
{
        int i;
        for (i=0 ; i<10 ; i++)
        {
                t[i]=rand();
                printf("%d-th element of array is equal %d\n",i,t[i]);
        }
        for (i=9 ; i>=0 ; i--)
        {
                t[i]=t[i-p];
                printf("&d-th after moving for %d places is equal %d\n",i,p,t[i]);
                if(i-p<0)
                {
                        t[i]=t['0'];
                }
        }
        return 0;
}

---

That's an array.

> void main()
main returns an int.
See the FAQ

> t[i]=t['0'];
You want 0, not '0'
If ASCII is your character set, then you've just read t[48], which is way outside your array.

Code:

---

scanf ("%d\n",&k);

instead

scanf ("%d",&k);

---

ssharish2005

Thanks for Your help. The code in such form is fully correct:

Code:

---

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

int przesun(int t[], int p);

main()
{
        int k;
        int w[10];
        printf ("Define, how many places you want to move values: ");
        scanf ("%d",&k);
        printf("\n");
        przesun (w,k);
}

int przesun (int t[], int p)
{
        int i;
        for (i=0 ; i<10 ; i++)
        {
                t[i]=rand();
                printf("%d-th element of array is equal %d\n",i,t[i]);
        }
                for (i=9 ; i>=0 ; i--)
        {
                if((i-p)<=0)
                {
                t[i]=0;
                printf("%d-th after moving for %d places is equal %d\n",i,p,t[i]);
                }
                else
                {
                t[i]=t[i-p];
                printf("%d-th after moving for %d places is equal %d\n",i,p,t[i]);
                }
        }
        return 0;
}

---

BUT I have one more question... how to define lenght of an array by giving a value? I mean I define an integer, write its value, and this integer is a length of an array.

Quote:

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BUT I have one more question... how to define lenght of an array by giving a value? I mean I define an integer, write its value, and this integer is a length of an array

---

you cant declare an array size at the run time. what u can do is use dynamic memeory allcation. sample code

Code:

---

#include<stdio.h>

int main()
{
    int *p;
    int size,i;
   
    printf("Array size : ");
    scanf("%d",&size);
   
    p = malloc(sizeof(int) * size);
   
    printf("Enter array values\n");
    for(i=0;i<size;i++)
        scanf("%d",&p[i]);
   
    printf("Array elements\n"); 
    for(i=0;i<size;i++)
        printf("%d\t",p[i]);
   
    getchar();
    return 0;
}
/*myoutput
Array size : 5
Enter array values
45
85
35
12
45
Array elements
45      85      35      12      45
*/

---

ssharish2005

Frankly, i don't understand what you mean. When I tried to use thiś malloc function, errors occured while compiling and nothing worked.

Perhaps you could
a) stop using a C++ compiler to compile C code
b) say something more useful that "it doesn't work" or "I get error messages".

By the way, ssharish2005 forgot to
#include <stdlib.h>
Perhaps that fixes one possible error message (if the error message was along the lines of converting an int to a pointer say)

Compiler writes following message : "error C2440: '=' : cannot convert from 'void *' to 'int *'" concerning such line of code :"p = malloc(sizeof(int) * size)".

And the error occurs even despite including stdlib.

> cannot convert from 'void *' to 'int *'"
Which means you're compiling your C code with a C++ compiler.

Rename your prog.cpp to be prog.c

And you should always check the return value of malloc, like so:

Code:

---

if((p = malloc(sizeof(int) * size)) == NULL)
    exit(1);
    /* And print a useful error message if you want */

---

In practice, malloc does not fail very often - for instance, it will fail if you run out of memory which for a lot of programs isn't very likely. However, if it does fail, it's definitely a bad thing and you should deal with it appropriately.

Also, if you've never used it before, it's worthwhile reading the documentation rather than just copy-pasting example code people give you. Even if the code is correct, you should take the time to understand the functions you are using.