Basic Calculator

Problem Statement

Given a string

representing a mathematical expression with parentheses, create a function to evaluate the expression and return the result as a number.

The valid operators in the expression are

, , , and . The expression may contain multiple spaces between operators and operands. The expression may also contain nested parentheses.

Your function should support non-negative integers and decimal numbers.

Rules and Constraints

• The input string
  s
  will only contain digits,
  +
  ,
  -
  ,
  *
  ,
  /
  , and parentheses. There will be at most one
  +
  ,
  -
  ,
  *
  , or
  /
  operator between each operand.
• The input string
  s
  is guaranteed to contain at least one operand and at most one
  +
  or
  -
  operator.
• There will not be any division by zero in the input string
  s
  .
• The input string
  s
  will not contain any invalid expressions that would cause a stack overflow.
• Your function should return a non-negative number as the result.

Output

Your function should return the result of the mathematical expression as a number. The result may be a decimal number if the input expression contains decimal points.

Example

Input: {"s":"1 + 1"} Output: 2