Merge Sort in C++

mergeSort.cpp

#include "mergeSort.h"



mergeSort::mergeSort(){}
mergeSort::~mergeSort(){}


void mergeSort::MergeSort(int a[], int n) {
	MergeSort(a, 0, n-1);

}
void mergeSort::MergeSort(int a[], int low, int high) {
	if (low >= high)return;
	else {
		int mid = (low + high) / 2;
		MergeSort(a, low, mid);
		MergeSort(a, mid + 1, high);
		Merge(a, low, mid, mid + 1, high);


	}

}
void mergeSort::Merge(int a[], int left_low, int left_high, int right_low, int right_high) {

	int len = right_high - left_low + 1;
	int *tmp = new int[len];
	int left = left_low;
	int right = right_low;
	for (int i = 0; i < len;i++) {
		if (left > left_high) {tmp[i] = a[right++];}
		else if (right > right_high) { tmp[i] = a[left++]; }
		else if (a[left] <= a[right]) { tmp[i] = a[left++]; }
		else { tmp[i] = a[right++]; }
	}
	for (int i = 0; i < len;i++) { a[left_low++] = tmp[i]; }
	delete tmp;

}

mergeSort.h

class mergeSort
{
public:
	mergeSort();
	~mergeSort();

	void MergeSort(int a[], int n);

private :
	void MergeSort(int a[], int low, int high);
	void Merge(int a[], int left_low, int left_high, int right_low, int right_high);
};

Good example, thanks!
I think this: delete tmp; should be more like this: delete[] tmp;