public class Solution
extends Object
150 - Evaluate Reverse Polish Notation\.
Medium
Evaluate the value of an arithmetic expression in [Reverse Polish Notation](http://en.wikipedia.org/wiki/Reverse_Polish_notation).
Valid operators are `+`, `-`, `*`, and `/`. Each operand may be an integer or another expression.
**Note** that division between two integers should truncate toward zero.
It is guaranteed that 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 <= 104
* `tokens[i]` is either an operator: `"+"`, `"-"`, `"*"`, or `"/"`, or an integer in the range `[-200, 200]`.