**Evaluate Reverse Polish Notation** ===================================== ### Problem Statement Given the **Reverse Polish Notation** (RPN) of an arithmetic expression as an array of strings, evaluate the expression. **Reverse Polish Notation** is a mathematical notation where operators follow their operands. The expression is evaluated by applying the operators from left to right. ### Input Constraints * The input `expressions` will be an array of strings `nums` and `operations`, representing the arithmetic expression in Reverse Polish Notation. * The input `expressions` will only contain the four basic arithmetic operators: `+`, `-`, `*`, `/`. * The input `expressions` will not contain any invalid characters or invalid operations. * The input `expressions` will only contain positive integers as operands. * The input `expressions` will always form a valid arithmetic expression. ### Output Constraints * The function should return the result of the arithmetic expression as a floating-point number. * The result should be accurate up to four decimal places. ### Time and Space Complexity * The function should have a time complexity of O(n), where n is the number of operations in the input array. * The function should have a space complexity of O(n), where n is the number of operations in the input array. ### Assumptions * The input `expressions` will always contain a valid stack-based RPN expression. * The input `expressions` will never contain any invalid characters or invalid operations. ### Example **Input:** {"tokens":["2","1","+","3","*"]} **Output:** 9