Merge sort implementation c++

Merge.cpp

#include <vector>
using namespace std;

vector<int> merge(vector<int> left, vector<int> right) {
	vector<int> sortedArray(left.size() + right.size(), 0);
	int k = 0;
	int i = 0;
	int j = 0;
	while (i < left.size() && j < right.size()) {
		if (left[i] <= right[j]) {
			sortedArray[k++] = left[i++];
		} else {
			sortedArray[k++] = right[j++];
		}
	}
	while (i < left.size()) sortedArray[k++] = left[i++];
	while (j < right.size()) sortedArray[k++] = right[j++];
	return sortedArray;
}

vector<int> mergeSort(vector<int> array) {
	if (array.size() <= 1) return array;
	int n = array.size();
	int mid = n / 2;
	vector<int> left(array.begin(), array.begin() + mid);
	vector<int> right(array.begin() + mid, array.end());
	return merge(mergeSort(left), mergeSort(right));
}