说明：  本程序用用实现如下操作，两个了栈共享向量空间v[m],它们的栈底分别设在数组两端，分别实现两个栈的相关入栈、出栈和取栈顶元素，的操作。
(with the procedures used to achieve the following operational, the two share a stack space vector v [m]. they stack the end located at both ends of the array, achieving two stacks of pushed out and take Zhanding stack elements of the operation.)