Heap Corruption Detected (C++) - c++

Question

I am having a problem with merge sorting. I'm using the code below, and I'm getting a heap corruption detected. It happens when I try to deallocate memory, so I would imagine I'm writing an out of bound index.
More specifically I think it's at the last for loop. When I print out the array, the first index is some garbage number, and the last index is actually the one before the last that I want. I've tried everything and I can't get around to solving this, can somebody tell me what exactly I'm doing wrong? 'Cause I can't seem to understand what the problem is.
Here's the code I'm using:
template <class T>
int Mergesort(T arr[], int n) {
MergeSortRec(arr, 0, n, n);
return 0;
}
template <class T>
void MergeSortRec(T arr[], int left, int right, int size) {
if(right > left) {
int mid = ((left + right) /2);
MergeSortRec(arr, left, mid, size);
MergeSortRec(arr, mid+1, right, size);
Merge(arr, left, mid, right, size);
}
return;
}
template <class T>
void Merge(T arr[], int left, int mid, int right, int size) {
int i = 0;
int j = left;
int k = mid + 1;
T* temp = new T[right - left];
while(j <= mid && k <= right) {
if(arr[j] < arr[k]) {
temp[i++] = arr[j++];
} else {
temp[i++] = arr[k++];
}
}
while(j <= mid) {
temp[i++] = arr[j++];
}
while(k <= right) {
temp[i++] = arr[k++];
}
for(int a = left; a <= right; a++) {
arr[a] = temp [a-left];
}
Cheers.

Answer 1

The problem is here:
T* temp = new T[right - left];
//...
for(int a = left; a <= right; a++) {
arr[a] = temp [a-left];
}
You allocate right-left elements, but the for loop steps through right-left+1 entries, so you run off the end of the array and trample on some memory you shouldn't. If you added delete [] temp; after that for loop (without it you are leaking memory!) you would probably see your error much earlier.
In fact, all your loops go one too far; it's just most obvious in this simple loop.