LeetCode150 Evaluate Reverse Polish Notation

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

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:

Based on the inverse Polish expression definition, set up the stack-up number

Traversing strings, encountering numbers, entering the stack, encountering operators, removing the top two elements of the stack, and then loading the results into the stack

Code:

1 classSolution {2  Public:3     intEVALRPN (vector<string>&tokens) {4stack<int>s;5          for(inti =0; i < tokens.size (); i++) {6             if(Tokens[i] = ="+"|| Tokens[i] = ="-"|| tokens[i]=="*"|| Tokens[i] = ="/") {7                 intNUM1 =s.top ();8 S.pop ();9                 intnum2 =s.top ();Ten S.pop (); One                 if(Tokens[i] = ="+") { A                     intnum = Num1 +num2; - s.push (num); -                 } the                 if(Tokens[i] = ="-") { -                     intnum = num2-NUM1; - s.push (num); -                 } +                 if(Tokens[i] = ="*") { -                     intnum = num2 *NUM1; + s.push (num); A                 } at                 if(Tokens[i] = ="/") { -                     intnum = num2/NUM1; - s.push (num); -                 } -             } -             Else { in S.push (Atoi (Tokens[i].c_str ())); -             } to         } +         intAns =s.top (); -         returnans; the     } *};

LeetCode150 Evaluate Reverse Polish Notation