0001 template <typename T> //对各自有序的[lo, mi)和[mi, hi)做归并
0002 void Vector<T>::merge( Rank lo, Rank mi, Rank hi ) { // lo < mi < hi
0003    Rank i = 0; T* A = _elem + lo; //合并后的有序向量A[0, hi - lo) = _elem[lo, hi)
0004    Rank j = 0, lb = mi - lo; T* B = new T[lb]; //前子向量B[0, lb) <-- _elem[lo, mi)
0005    for ( Rank i = 0; i < lb; i++ ) B[i] = A[i]; //复制出A的前缀
0006    Rank k = 0, lc = hi - mi; T* C = _elem + mi; //后缀C[0, lc) = _elem[mi, hi)就地
0007    while ( ( j < lb ) && ( k < lc ) ) //反复地比较B、C的首元素
0008       A[i++] = ( B[j] <= C[k] ) ? B[j++] : C[k++]; //将更小者归入A中
0009    while ( j < lb ) //若C先耗尽，则
0010       A[i++] = B[j++]; //将B残余的后缀归入A中——若B先耗尽呢？
0011    delete[] B; //释放临时空间：mergeSort()过程中，如何避免此类反复的new/delete？
0012 }