Evaluate the value of an arithmetic expression in .

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

 

class Solution {    public int evalRPN(String[] tokens) {        Stack
     
       stack =new Stack<>();        for(String s:tokens){            if(s.equals("+")){                int a=stack.pop();                int b=stack.pop();                stack.push(a+b);            }else if(s.equals("-")){                int a=stack.pop();                int b=stack.pop();                stack.push(b-a);            }else if(s.equals("*")){                int a=stack.pop();                int b=stack.pop();                stack.push(a*b);            }else if(s.equals("/")){                int a=stack.pop();                int b=stack.pop();                stack.push(b/a);            }else{                stack.push(Integer.parseInt(s));            }        }        return stack.pop();    }}