中缀变后缀表达式求值：输入表达式，#为结束符(如1+2#），程序会自动给出后缀表达式，并给出最终计算结果。程序中部分地方有注释-Variable postfix infix expression evaluation: Enter the expression,# to end the character (eg, 1+2#), the program will automatically give postfix expression, and gives the end result. Some parts of the program annotated