下面的C++代码实现归并排序。代码在执行时，将输出一次HERE字符串，因为merge()函数仅被调用一次。
void merge(std::vector<int>& arr, int left, int mid, int right) { std::vector<int> temp(right - left + 1); int i = left; int j = mid + 1; int k = 0; while (i <= mid && j <= right) { if (arr[i] <= arr[j]) { temp[k++] = arr[i++]; } else { temp[k++] = arr[j++]; } } while (i <= mid) { temp[k++] = arr[i++]; } while (j <= right) { temp[k++] = arr[j++]; } for (int p = 0; p < k; ++p) { arr[left + p] = temp[p]; }} void mergeSort(std::vector<int>& arr, int left, int right) { if (left >= right) { return; } int mid = left + (right - left) / 2; mergeSort(arr, left, mid); mergeSort(arr, mid + 1, right); std::cout << "HERE"; merge(arr, left, mid, right);}