Evaluate Reverse Polish Notation

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

valid operators Are + ,  -,  * ,  /. Each operand is an integer or another expression.

Some Examples:

  ["2", "1", "+", "3", "*")--((2 + 1) (3)-9  ["4", "", "5", "/", "+"], 4 + (13/5))

Class Solution {public:    int evalrpn (vector<string> &tokens) {        stack<int> data;        int i,len=tokens.size ();        int op_data1,op_data2;        for (i=0;i<len;i++) {            if (tokens[i]!= "+" && tokens[i]!= "-" && tokens[i]!= "*" && tokens[i ]!= "/")                 Data.push (Atoi (Tokens[i].c_str ()));            else{                op_data2=data.top ();                Data.pop ();                Op_data1=data.top ();                Data.pop ();                if (tokens[i]== "+") Data.push (OP_DATA1+OP_DATA2);                if (tokens[i]== "-") Data.push (OP_DATA1-OP_DATA2);                if (tokens[i]== "*") Data.push (OP_DATA1*OP_DATA2);                if (tokens[i]== "/") Data.push (OP_DATA1/OP_DATA2);            }        }        return Data.top ();    }};

Evaluate Reverse Polish Notation