C Pointer to an Array example stops working - c

Question

I'm working on an example and my code is stopped woking when I run it.(Note that I translated the question to English so sorry for grammar mistakes.)
Here is the question:
myShrink() function's prototype is like this:
void myShrink(int *param1, const int param2);
myShrink() function should find the average of the array param1 then should increment the element by 1 if its less than average, or should decrement the element by 1 if it's more than average. param2 is a number of elements in an array.
Here is the content of the main() function:
void myStretch(int *param1, const int param2);
int main () { int myArray[] = {2, 4, 2, 4, 2, 4};
int index;
myStretch(myArray, 6);
printf("UPDATED ARRAY: ");
for(index = 0; index < 6; index++){
printf("%d\t", myArray[index]);
}
return 0;
}
---------The result when we run the program:-----
UPDATED ARRAY: 1 5 1 5 1 5
Now this was the question part what we need to is basically programming the content of myShrink() function and here is my work:
void myShrink(int *param1, const int param2)
{
int array[param2];
param1=array;//Using pointer to point elements of array
int average=0;
int i,j;
for(i=0;i<param2;i++)
{
average+=*(param1 + i);//Adding each element of array
}
average=average/param2;//Then dividing result to param2 to find average
for(j=0;j<param2;j++)
{
if(*(param1+j)<average)//if below average
{
*(param1+j)+=1;//increment
}
else if(*(param1+j)>average)//if above average
{
*(param1+j)-=1;//decrement
}
}
}
But its stops working when I run it. Where I did make mistake and how can I fix it?

Answer 1

Just do this:
#include<stdio.h>
void myStretch(int *param1, const int param2);
int main () { int myArray[] = {2, 4, 2, 4, 2, 4};
int index;
myStretch(myArray, 6);
printf("UPDATED ARRAY: ");
for(index = 0; index < 6; index++){
printf("\n%d\t", myArray[index]);
}
return 0;
}
void myStretch(int *param1, const int param2)
{
int average=0;
int i,j;
for(i=0;i<param2;i++)
{
average+=*(param1 + i);//Adding each element of array
}
average=average/param2;//Then dividing result to param2 to find average
for(j=0;j<param2;j++)
{
if(*(param1+j)<average)//if below average
{
(*(param1+j))+=1;//increment
}
else if(*(param1+j)>average)//if above average
{
printf("%d ",(*(param1+j)));
(*(param1+j))-=1;//decrement
}
}
}
Now first thing: your result is wrong. It should be 3 3 3 3 3 3. As the average in this case is 3 and therefore 2 will become 3 and 4 will also become 3. Secondly you don't have to assign a new array inside the function. Just do it this way. Third mistake:
*(param1+j)>average
should be replaced by
(*(param1+j))>average
and similarly for less than sign.
UPDATE: Also note that many people argue that array[param2] is legal or not. When you declare such an array they are called Variable Length Array(VLA). This is allowed in modern C compilers but older compilers like Turbo C don't allow.

Answer 2

In below myShrink function, after 'param1=array;' statement param1 start pointing to array which has garbage inside.
void myShrink(int *param1, const int param2){
int array[param2];
param1=array;//Using pointer to point elements of array
int average=0;
int i,j;
//debug code to shows param1 points to array which has garage inside
int index =0 ;
for(index = 0; index < 6; index++){
printf("myDebug: %d\n", param1[index]);
}
for(i=0;i<param2;i++)
{
average+=*(param1 + i);//Adding each element of array
}
average=average/param2;//Then dividing result to param2 to find average
for(j=0;j<param2;j++)
{
if(*(param1+j)<average)//if below average
{
*(param1+j)+=1;//increment
}
else if(*(param1+j)>average)//if above average
{
*(param1+j)-=1;//decrement
}
}}