Evaluate Reverse Polish Notation
Detailed guide and Python implementation for the 'Evaluate Reverse Polish Notation' problem.
Problem Statement
You are given an array of strings tokens that represents an arithmetic expression in Reverse Polish Notation.
Evaluate the expression and 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 reverse polish notation.
Write a function evalRPN(tokens: List[str]) -> int.
- •1 <= len(tokens) <= 10^4
- •tokens[i] is either an operator (+, -, *, /) or an integer in the range [-200, 200]
Examples
tokens = ["2", "1", "+", "3", "*"]
9
((2 + 1) * 3) = 9.
tokens = ["4", "13", "5", "/", "+"]
6
(4 + (13 / 5)) = (4 + 2) = 6. Note 13/5 truncates to 2.
tokens = ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"]
22
((10 * (6 / ((9 + 3) * -11))) + 17 + 5) = 22.
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
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