Merge Sort - Segmentation Error

I've been programming in Python for more than a year now, and I just moved back to C++, to learn a few basic algorithms. I started with merge sort, but it gives me a segmentation errror. Help would be greatly appreciated. I think I debugged where it happens, but I'm unable to understand why.

```#include <iostream>
using namespace std;
void* merge(int array1[], int array2[], int low, int mid, int high){
int i, j, k;
for (i = low,j = mid, k = low; i < mid, j < high; k++){
if (array1[i] < array1[j]){
array2[k] = array1[i];
i++;
}
else{
array2[k] = array1[j];
j++;
}
}
if (i == mid){
for (; j < high; j++, k++){
array2[k] = array1[j];
}
}
else{
for (; i < mid; i++, k++){
array2[k] = array1[i];
}
}
void* merge_sort(int array1[], int copy[], int low, int high){
int mid;
int range = high - low;
if (range == 1)
copy[low] = array1[low];
else{
mid = low + range/2;
merge_sort(array1, copy, low, mid);
// Segmentation error seems to be here.
merge_sort(array1, copy, mid, high);
}
merge(array1, copy, low, mid, high);
}

int main()
{
int n, temp;
cout << "How many numbers do you want to enter?" << endl;
cin >> n;
int numarray[n];
for (int i = 0; i < n; i++){
cin >> numarray[i];
}
int dumarray[n];  // Used for filling elements from merge sort
merge_sort(numarray, dumarray, 0, n);
cout << "Merge Sort" << endl;
for (int i = 0; i < n; i++){
cout << dumarray[i] << endl;
}
return 0;
}
```

EDIT:

```#include <iostream>
using namespace std;

void merge_sort(int [], int [], int, int);

void merge(int array1[], int array2[], int low, int mid, int high){
int i, j, k;
for (i = low,j = mid, k = low; i < mid, j < high; k++){
if (array1[i] < array1[j]){
array2[k] = array1[i];
i++;
}
else{
array2[k] = array1[j];
j++;
}
}
if (i == mid){
for (; j < high; j++, k++){
array2[k] = array1[j];
}
}
else{
for (; i < mid; i++, k++){
array2[k] = array1[i];
}
}
}

void merge_sort(int array1[], int copy[], int low, int high){
int mid;
int range = high - low;
mid = low + range/2;
if (range == 1)
copy[low] = array1[low];
else{
mid = low + range/2;
merge_sort(array1, copy, low, mid);
merge_sort(array1, copy, mid, high);
merge(array1, copy, low, mid, high);
}
}
int main(){
int n, temp;
cout << "How many numbers do you want to enter?" << endl;
cin >> n;
int numarray[n];
for (int i = 0; i < n; i++){
cin >> numarray[i];
}
int dumarray[n];
merge_sort(numarray, dumarray ,0, n);
for (int i = 0; i < n; i++){
cout << dumarray[i] << endl;
}

}
```

The calculation for mid value seems to be wrong. Try calculating mid as

mid = low + (high-low)/2

Edit: Move merge(array1, copy, low, mid, high);inside the else bracket.

```else
{
mid = low + range/2;
merge_sort(array1, copy, low, mid);
merge_sort(array1, copy, mid, high);
merge(array1, copy, low, mid, high);
}
```

The merge function also has a lot of bugs. The condition check in the initial for loop i < mid, j < high is separated by a comma which means it is only checking for j < high and discarding condition check for i.