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