cpp-flashcards/org/study_deck_02/dsa/stack/0150-evaluate-reverse-polish-notation.org

#+PROPERTY: STUDY_DECK_02
* TODO 0150. Evaluate Reverse Polish Notation :medium:
:PROPERTIES:
:NEETCODE: [[file:../../roadmap.org::*0150. Evaluate Reverse Polish Notation][0150. Evaluate Reverse Polish Notation]]
:END:

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.

*Example 1:*


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


*Example 2:*


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


*Example 3:*


#+begin_src
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
#+end_src


*Constraints:*

 - ~1 <= tokens.length <= 10^{4}~

 - ~tokens[i]~ is either an operator: ~"+"~, ~"-"~, ~"*"~, or ~"/"~, or an integer in the range ~[-200, 200]~.

** TODO Approach
Write your approach here.

** TODO Python
#+begin_src python
class Solution:
    def evalRPN(self, tokens: List[str]) -> int:
#+end_src

** TODO C++
#+begin_src cpp
class Solution {
public:
    int evalRPN(vector<string>& tokens) {
        
    }
};
#+end_src