完成了α-β剪枝的功能，从文件中读入每个结点的极大极小值以及各个父子结点的关系，然后进行剪枝，输出被剪枝结点的信息-Completion of the α-β pruning function, read from the file of each node as well as the minimax value of each node of the relationship between father and son, and then proceed to cut output by node pruning information