Evaluate the value of an arithmetic expression in Reverse Polish Notation.



Valid operators are +, -, *, /. Each operand may be an integer or another expression.



Some examples:



[ 2 , 1 , + , 3 , * ] -> ((2 + 1) * 3) -> 9

[ 4 , 13 , 5 , / , + ] -> (4 + (13 / 5)) -> 6

分析：这一题就是写程序计算逆波兰式的结果，遍历表达式，碰到操作数入栈，碰到操作符就从栈顶取出两个操作数，再将计算后的结果入栈，最后栈中剩余的唯一操作数就是计算结果。-. Evaluate the value of an arithmetic expression in Reverse Polish Notation Valid operators are+,-,*,/Each operand may be an integer or another expression Some examples:.. [" 2" , " 1" , " +" , "　3 " ," * " ]->　((2+ 1)* 3)->　9 ["　4 " ,"　13 " ,"　5 " ," /" ," + " ]->　(4+ (13/After this problem is to write a program to calculate the inverse Polish results, iterate expression operand stack encounter, encounter operator to fetch two operands　the stack, and then calculated as follows:>　6 Analysis- 5)) The results of the stack, the only remaining operand stack is the final calculations.