本设计属于二叉树的应用，即使用二叉树计算表达式的值，要求将表达式（例如9*7+6/3等）以二叉树方式存入数组，以递归的方式建立表达式之二叉树结构，再分别输出前序遍历、中序遍历和后序遍历结果，并计算出表达式的结果。-This design is the application of the binary tree, using the binary tree to calculate the value of the expression, the expression (9* 7+6/3, etc.) to the way binary tree into an array, the recursive expression of binary tree structure, and then output to pre-order traversal, traversal and postorder traversal results, and calculate the results of the expression.