Saving integers from a file into an array - c

Question

I was hoping to get a bit of help, I am implementing an inversion counter algorithm to take in 50,000 intergers and display the inversions and time it took to run the algorithm, I am having a hard time allocating and saving the integers from the file into an array. My code complies and runs but nothing happens
here is what I have:
int main(int argc, char** argv)
{
int n, i;
int inversions=0;
int *A;
FILE *file;
char filename[100];
clock_t start, end;
double totalTime;
printf("Enter filename: ");
scanf("%s", filename);
file = fopen(filename, "r");
if(file == NULL)
{
printf("Error opening file!\n");
return 0;
}
fscanf(file, "%d", &n);
A = (int*) malloc(n * sizeof(int));
for(i = 0; i < n; i++) {
fscanf(file, "%d", &A[i]);
}
start = clock();
inversions = countInversionsBruteForce(A, n);
end = clock();
totalTime = (double) (end - start) / CLOCKS_PER_SEC;
printf("Brute Force Algorithm\n");
printf("Number of inversions: %d\n", inversions);
printf("Execution time: %f\n", totalTime);
I think I have noth allocated array size and saved it properly

Answer 1

Your program is incomplete so I was not able to compile it. Minimized the problem to just loading the data into your array:
Formatted code for readability.
Generated a suitable input file. Most likely this is your problem but you have not shared your input sample with us.
Added missing include files.
Remove argc, argv as you not using them.
Minimize scope of variables. Use size_t instead of int for unsigned values.
Max string size on obtaining file name
Check return value for scanf(), fopen(), fscanf().
Printing out the data read to demonstrate it's working.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main() {
printf("Enter filename: ");
char filename[100];
if(scanf("%99s", filename) != 1) {
printf("scanf failed\n");
return 1;
}
FILE *file = fopen(filename, "r");
if(!file) {
printf("Error opening file!\n");
return 1;
}
size_t n;
fscanf(file, "%zu", &n);
if(!n) {
printf("n must be positive");
return 1;
}
int *A = malloc(n * sizeof(*A));
for(size_t i = 0; i < n; i++)
if(fscanf(file, "%d", &A[i]) != 1) {
printf("fscanf() failed\n");
return 1;
}
printf("n = %zu\n", n);
printf("A = ");
for(size_t i = 0; i < n; i++)
printf("%d%s", A[i], i + 1 < n ? ", " : "\n");
}
with 1.txt as:
4
1
2
3
4
a sample session looks like this:
Enter filename: 1.txt
n = 4
A = 1, 2, 3, 4