Changing **array + a to *array[a] - c

Question

What my program does is it finds 2 numbers of an array that are closest to the average, one is bigger, one is smaller. It works fine, however I need to change for example **array+a to *array[a].
However, when I load the program, it crashes after I input the numbers. If I try to print *array[0], *array[1], etc. it works fine. When I try to print or just do something with *array[a], *array[b], it crashes. Thank you for your help.
#include <stdio.h>
#include <stdlib.h>
int input (int *t, int *array[]);
void calculation (int *array[], int *t, int *x, int *y);
void output (int *x, int *y);
int main()
{
int *array, t, x, y;
input (&t, &array);
calculation (&array, &t, &x, &y);
output (&x, &y);
return 0;
}
int input (int *t, int *array[])
{ int n, *ptr;
printf ("How big is the array?");
scanf ("%d", &n);
ptr = (int*) malloc(n * sizeof(int));
int k;
printf ("Enter the numbers:");
for (k=0; k<n; k++)
{ scanf ("%d", ptr + k);
}
*t=n;
*array=ptr;
return 0;
}
void calculation (int *array[], int *t, int *x, int *y)
{ float sum=0, avg;
int min, max;
int more, less;
int a, b, c;
for (a=0; a<(*t); a++)
{sum=sum+ **array + a;
}
avg=sum/(*t);
min= *array[0];
max= *array[0];
for (b=0; b<(*t); b++)
{ if (max < (**array + b)) max=(**array + b);
if (min > (**array + b)) min=(**array + b);
}
more=max;
less=min;
for (c=0; c<(*t); c++)
{ if (((**array + c) < avg) && ((**array + c) > less)) less=(**array + c);
if (((**array + c) > avg) && ((**array + c) < more)) more=(**array + c);
}
*x=less;
*y=more;
}
void output (int *x, int *y)
{ printf("Number that is less than the average:%d\n", *x);
printf("Number that is more than the average:%d\n", *y);
}

Answer 1

It would be better to rethink your function prototypes a bit. It makes sense to pass a pointer to array to the input() function since you are allocating memory for it, and you want to be able to access it when you return. But you don't need to pass in the pointer to int t; instead, just return the value of n, and assign it to t in main.
There is no reason to pass a pointer to array to the function calculation(), since you are not changing the array allocation. You can also pass in the value of t from main(), since you only use this value in calculation(), but do not change it.
Similarly, the output() function only needs copies of x and y, since it does not change them.
The rule of thumb here is that you pass a pointer to a value into a function when you want to modify the value inside the function and have access to the modified value in the calling function. But you can also return a value instead of using a pointer to it.
These changes do not alter the functionality of your code, but they substantially improve its readability. You even get a sense of what is being modified in each function just by looking at the function prototypes. Well, the changes do alter the functionality in that your original **array + a was incorrect, and needed to be either *(*array + a) or (*array)[a]. But sorting that problem out should help you to appreciate the virtue of the simpler function prototypes. Here is the modified code:
#include <stdio.h>
#include <stdlib.h>
int input(int *array[]);
void calculation(int array[], int t, int *x, int *y);
void output(int x, int y);
int main(void)
{
int *array, t, x, y;
t = input(&array);
calculation(array, t, &x, &y);
output(x, y);
return 0;
}
int input(int *array[])
{ int n, *ptr;
printf("How big is the array?");
scanf("%d", &n);
ptr = (int*) malloc(n * sizeof(int));
int k;
printf("Enter the numbers:");
for (k=0; k<n; k++)
{ scanf("%d", ptr + k);
}
*array=ptr;
return n;
}
void calculation(int array[], int t, int *x, int *y)
{ float sum=0, avg;
int min, max;
int more, less;
int a, b, c;
for (a=0; a<t; a++)
{sum=sum+ array[a];
}
avg=sum/t;
min= array[0];
max= array[0];
for (b=0; b<t; b++)
{ if (max < array[b]) max=array[b];
if (min > array[b]) min=array[b];
}
more=max;
less=min;
for (c=0; c<t; c++)
{ if ((array[c] < avg) && (array[c] > less)) less=array[c];
if ((array[c] > avg) && (array[c] < more)) more=array[c];
}
*x=less;
*y=more;
}
void output(int x, int y)
{ printf("Number that is less than the average:%d\n", x);
printf("Number that is more than the average:%d\n", y);
}

Answer 2

Just like BLUEPIXY and Some programmer dude said, it's supposed to be (*array)[a]