Leetcode:evaluate Reverse Polish Notation

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

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

Some Examples:

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

Analysis: Reverse Polish notation can be obtained by post traversal compute tree, we can evaluate its value through the stack, the code is as follows:

1 classSolution {2  Public:3     intEVALRPN (vector<string> &tokens) {4         intresult =0;5stack<int>S;6         7          for(inti =0; I < tokens.size (); i++){8             if(Is_operator (Tokens[i])) {9                 intRV =s.top ();Ten S.pop (); One                 intLV =s.top (); A S.pop (); -                 if(Tokens[i] = ="+") -S.push (LV +RV); the                 Else if(Tokens[i] = ="-") -S.push (LV-RV); -                 Else if(Tokens[i] = ="*") -S.push (LV *RV); +                 Else if(Tokens[i] = ="/") -S.push (LV/RV); +}Else{ A S.push (Atoi (Tokens[i].c_str ())); at             } -         } -         returns.top (); -     } -      -     BOOLIs_operator (strings) { in         returns = ="+"|| s = ="-"|| s = ="*"|| s = ="/"; -     } to};

Leetcode:evaluate Reverse Polish Notation