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).
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Valid operators are `+`, `-`, `*`, and `/`. Each operand may be an integer or another expression.
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**Note** that division between two integers should truncate toward zero.
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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.
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**Example 1:**
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Input: tokens = ["2","1","+","3","*"]
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Output: 9
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Explanation: ((2 + 1) * 3) = 9
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**Example 2:**
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Input: tokens = ["4","13","5","/","+"]
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Output: 6
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Explanation: (4 + (13 / 5)) = 6
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**Example 3:**
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Input: tokens = ["10","6","9","3","+","-11","*","/","*","17","+","5","+"]
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Output: 22
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Explanation: ((10 * (6 / ((9 + 3) * -11))) + 17) + 5
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= ((10 * (6 / (12 * -11))) + 17) + 5
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= ((10 * (6 / -132)) + 17) + 5
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= ((10 * 0) + 17) + 5
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= (0 + 17) + 5
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= 17 + 5
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= 22
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**Constraints:**
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* `1 <= tokens.length <= 104`
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* `tokens[i]` is either an operator: `"+"`, `"-"`, `"*"`, or `"/"`, or an integer in the range `[-200, 200]`. |