evaluate-reverse-polish-notation

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

class Solution {
public:
    int evalRPN(vector<string> &tokens) {
        int len = tokens.size();
        stack<int> s;
        
        for(vector<string>::size_type i = 0;i < tokens.size(); i++){
            if(tokens[i] == "+" || tokens[i] == "-"
              || tokens[i] == "*" || tokens[i] == "/"){
                int op2 = s.top();
                s.pop();
                int op1 = s.top();
                s.pop();
                s.push(op(op1,op2,tokens[i]));
            }else{
                s.push(stoi(tokens[i]));
            } 
        }
        
        return s.top();
        
    }
    
    int op(int op1,int op2,string optor){
        if(optor == "+")
            return op1+op2;
        else if(optor == "-")
            return op1-op2;
        else if(optor == "*")
            return op1*op2;
        else if(optor == "/")
            return op1/op2;
        
        return 0;
    }
};