### 150. Evaluate Reverse Polish Notation#

Evaluate the value of an arithmetic expression in Reverse Polish Notation.

Valid operators are

`+`

,`-`

,`*`

, and`/`

. Each operand may be an integer or another expression.

Note:

- Division between two integers should truncate toward zero.
- The given RPN expression is always valid. That means the expression would always evaluate to a result, and there will not be any division by zero operation.

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)) = 6`

Example 3:`Input: tokens = ["10","6","9","3","+","-11","*","/","*","17","+","5","+"] Output: 22 Explanation: ((10 * (6 / ((9 + 3) * -11))) + 17) + 5 = ((10 * (6 / (12 * -11))) + 17) + 5 = ((10 * (6 / -132)) + 17) + 5 = ((10 * 0) + 17) + 5 = (0 + 17) + 5 = 17 + 5 = 22`

Constraints:

`1 <= tokens.length <= 10^4`

`tokens[i]`

is either an operator:`"+", "-", "*", "/"`

or an integer in the range`[-200, 200]`

.

Reverse Polish Notation (RPN):Reverse Polish notation is a postfix mathematical notation in which every operator follows all of its operands.

- It is also known as postfix notation.
- It does not need any parentheses as long as each operator has a fixed number of operands.
- The RPN expression
`(1 + 2) * (3 + 4)`

can be written as`( ( 1 2 + ) ( 3 4 + ) * )`

in RPN.