Evaluate Reverse Polish Notation

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Problem Statement

You are given an array of strings tokens that represents an arithmetic expression in a Reverse Polish Notation .

Evaluate the expression. Return an integer that represents the value of the expression .

Note that:

The valid operators are '+' , '-' , '*' , and '/' .

Each operand may be an integer or another expression.

The division between two integers always truncates toward zero .

There will not be any division by zero.

The input represents a valid arithmetic expression in a reverse polish notation.

The answer and all the intermediate calculations can be represented in a 32-bit integer.

Examples

Example 1

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

Example 2

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

Example 3

Input: tokens = ["10","6","9","3","+","-11","*","/","*","17","+","5","+"]
Output: 22
((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 "/" , or an integer in the range [-200, 200] .

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicMath