39 lines
1.2 KiB
Markdown
39 lines
1.2 KiB
Markdown
|
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]`.
|