You are given tokens , an array of strings that forms an arithmetic expression in Reverse Polish Notation (postfix). Each token is either an integer or one of the operators + , - , * , / . Evaluate the expression and return the resulting integer. The two operands of an operator are the two most recently seen values, in left-to-right order. Division truncates toward zero (so 13 / 5 is 2 and -7 / 2 is -3 ). Input format Input is [tokens] , e.g. [[ 2 , 1 , + , 3 , * ]] .