Evaluate Reverse Polish Notation

You are given an array of strings tokens that represents an arithmetic expression in Reverse Polish Notation (postfix notation).

Evaluate the expression and return the result as an integer.

Valid operators are +, -, *, and /. Each operand can be either an integer or another expression. Division truncates toward zero (not floor division). The answer is guaranteed to fit in a 32-bit integer.

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Example 1

Input: tokens = ["2", "1", "+", "3", "*"]
Output: 9
Explanation: ((2 + 1) * 3) = 9

Example 2

Input: tokens = ["4", "13", "5", "/", "+"]
Output: 6
Explanation: (4 + (13 / 5)) = (4 + 2) = 6

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Constraints

• 1 <= tokens.length <= 10^4
• tokens[i] is either an operator "+", "-", "*", or "/", or an integer in the range [-200, 200].
• The input is always a valid Reverse Polish Notation expression.
• The result will always fit in a 32-bit signed integer.