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