storing input into malloc array (1d and 2d) and printing - c

Question

I am tryin to take input from the user and store it into an array and print it out: i have 2 functions:
/* Read a vector with n elements: allocate space, read elements,
return pointer */
double *read_vector(int n){
double *vec = malloc(n * sizeof(double));
int i;
for (i = 0; i < n; i++)
vec[i] = n;
return vec;
}
and the print function is:
void print_vector(int n, double *vec){
int i;
for (i = 0; i < n; i++) {
printf("%d\n", vec[i]);
}
}
the main function is:
#include <stdio.h>
#include <stdlib.h>
double *read_vector(int n);
void print_vector(int n, double *vec);
void free_vector(double *vec);
int main(){
int n;
double *vector;
/* Vector */
printf("Vector\n");
printf("Enter number of entries: ");
scanf("%d", &n);
printf("Enter %d reals: ", n);
vector = read_vector(n);
printf("Your Vector\n");
print_vector(n,vector);
free_vector(vector);
}
when i run this, it does not let me enter any numbers, it just skips it and prints out 0's. How do i fix this?

Answer 1

Try the code below. You're almost certainly either not compiling with warnings, or ignoring the warnings. All warnings mean something, and to a beginner they all matter. With gcc use the -Wall option, or even -pedantic.
As halfelf pointed out, you need a scanf in your read loop but it needs to be a pointer (&vec[i]). Always return something at the end of main. Also check the return value of malloc, it could fail and return a null pointer.
#include <stdio.h>
#include <stdlib.h>
double *read_vector(int n)
{
double *vec = malloc(n * sizeof(double));
int i;
for (i = 0; i < n; i++) {
printf("Enter number %i of %i: ", i + 1, n);
scanf("%lf", &vec[i]);
}
return vec;
}
void print_vector(int n, double *vec)
{
int i;
for (i = 0; i < n; i++) {
printf("%f\n", vec[i]);
}
}
void free_vector(double *vec)
{
free(vec);
}
int main()
{
int n;
double *vector;
printf("Vector\n");
printf("Enter number of entries: ");
scanf("%i", &n);
vector = read_vector(n);
printf("Your Vector\n");
print_vector(n, vector);
free_vector(vector);
return 0;
}

Answer 2

In the read_vector(int n) function's for loop:
for (i=0; i<n; i++)
vec[i] = n; // this should be scanf("%lf",vec+i) to read input from stdin
and notice your { and } there. If there's only one line in the loop, { and } is not necessary, OR you have to use a pair of them. The return clause must be out of the loop.
Btw, add return 0 at the end of your main function.

Answer 3

simple..you forgot to write scanf..!
double *read_vector(int n)
{
double *vec = malloc(n * sizeof(double));
int i;
for (i = 0; i < n; i++)
scanf("%d",&vec[i]);
return vec;
}