dynamic allocation - pointer to pointer in c - c

Question

i got exercise from school.
I need to write a function that get array of grades, the size of the array, int number that represent the range of the grades, array that represent the count of the number of the grades in the same range and array that sum the grade of in the range.
the function will create sub groups to the grades, for exmaple: if the range of the grades is 10 so that sub groups is: 0-9, 10-19, 20-29, 30-39,...,90-99,100.
the range is 10 so the number of the sub-groups is 100/range + 1 (11 in that example which the range is 10).
the function will return array that is pointer to pointer, each element in this array will represent the sub-group by ASC.
if there is no values in the range (sub-group) we need to set NULL.
the count array will count the number of the grade in the same range,
and the sum array will sum those grades.
we can assume that the size of those arrays are also 100/range + 1.
important: i need to use dynamic allocate memroy.
i think i have the problem to calculate to which index in the range i need to put the grade, it work in some cases, but not to all.
examples:
int grades[SIZE_GRADES] = {98,45,77,65,89,90,100,43,54,67,55,88,76,67,33,23,45,76,72,76};
int avg_grd1[100 / GRD_RANGE1 + 1];
int avg_grd2[100 / GRD_RANGE2 + 1];
int count_grd1[100 / GRD_RANGE1 + 1];
int count_grd2[100 / GRD_RANGE2 + 1];
int** arr1 = GradeStat(grades, SIZE_GRADES, GRD_RANGE1, count_grd1, avg_grd1);
int** arr2 = GradeStat(grades, SIZE_GRADES, GRD_RANGE2, count_grd2, avg_grd2);
#define GRD_RANGE1 10
#define GRD_RANGE2 7
#define SIZE_GRADES 20
those are working for me.
but what i insert this arrays it didn't: (same vars, just different array).
int grades[SIZE_GRADES] = { 45,46,58,68,70,73,74,78,90,94 };
#define GRD_RANGE1 10
#define GRD_RANGE2 15
#define SIZE_GRADES 10
and that's my code:
int** GradeStat(int* Grades, int size_grades, int grd_range, int* count_grd, int* avg_grd)
{
int sub_range = 100 / grd_range + 1;
int** class_grd;
int place_in_sub_range;
// alocate memory.
class_grd = (int**)calloc(sub_range, sizeof(int));
if (class_grd == NULL) {
exit(1);
}
for (int i = 0; i < sub_range; i++) {
count_grd[i] = 0;
}
for (int i = 0; i < sub_range; i++) {
avg_grd[i] = 0;
}
for (int i = 0; i < SIZE_GRADES; i++) {
// the index (place) in the pointer of pointer.
place_in_sub_range = Grades[i] / grd_range;
if (place_in_sub_range <= sub_range) {
// create new pointer that relevant to the range.
if (class_grd[place_in_sub_range] == 0) {
// alocate memory, set the grade and set the address of the pointer inside the pointer to pointer array.
int* sub_range_pointer = (int*)calloc(1, sizeof(int));
if (sub_range_pointer == NULL) {
exit(1);
}
// save the grade in the memory.
*sub_range_pointer = Grades[i];
// set the pointer address in the poinet of pointer array.
class_grd[place_in_sub_range] = sub_range_pointer;
// count the number of grades in each range.
count_grd[place_in_sub_range]++;
// set the grade in the sum array.
avg_grd[place_in_sub_range] = Grades[i];
}
else {
// find out how many elemnts is exist, realloc + add new grade and add the grade to there.
int* sub_range_pointer = (int*)realloc(class_grd[place_in_sub_range], count_grd[place_in_sub_range] * sizeof(int) + sizeof(int));
if (sub_range_pointer == NULL) {
exit(1);
}
// set the grade in the relevant range.
sub_range_pointer[count_grd[place_in_sub_range]] = Grades[i];
// set the pointer address in the poinet of pointer array.
class_grd[place_in_sub_range] = sub_range_pointer;
// raise the number of grades in the relevant range.
count_grd[place_in_sub_range]++;
// set the grade in the sum array.
avg_grd[place_in_sub_range] = (avg_grd[place_in_sub_range] + Grades[i]) / 2;
}
}
//else {
// return NULL;
//}
}
for (int i = 0; i < sub_range; i++) {
if (class_grd[i] == 0) {
class_grd[i] = NULL;
}
}
// return the pointer of pointer array.
return class_grd;
so on arr1 my code is working,
but on the arr2 it isn't.
i see that when i take the 45 or 46 grade and divine it in the range i'm inserting it to the 3 index (and it should be the second).
When I'm running the code through the school test checker i get this error:
timeout: the monitored command dumped core ../runTrain.sh: line 1: 21344 Segmentation fault timeout -k 5s 5s ./MainTrain.exe > ./mainTrain.log