Evaluate Reverse Polish Notation

Evaluate Reverse Polish Notation

Problem:

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

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

Ideas:

Classic Application of Stacks

My Code:

 Public classSolution { Public intEVALRPN (string[] tokens) {if(Tokens = =NULL|| Tokens.length = = 0)return0; Stack<Integer> stack =NewStack<integer>();  for(inti = 0; i < tokens.length; i++) {String str=Tokens[i]; if(Isoperator (str)) {intone =Stack.pop (); intboth =Stack.pop ();            Stack.push (GetResult (one, one, str)); }            Else{stack.push (integer.valueof (str)); }        }        returnStack.isempty ()? 0: Stack.pop (); }     Public intGetResult (intOneintBoth , String str) {        Switch(str) { Case"+":returnOne +both ;  Case"-":returnOne-both ;  Case"*":returnOne *both ;  Case"/":returnOne/both ; }        return0; }     Public Booleanisoperator (String str) {if(Str.equals ("+") | | str.equals ("-") | | str.equals ("*") | | str.equals ("/"))return true; return false; }}

View Code

Evaluate Reverse Polish Notation