Evaluate Reverse Polish Notation — Medium Coding Interview Question

You are given an array of strings tokens representing an arithmetic expression in Reverse Polish Notation (postfix). Evaluate the expression and return the result as an integer. Valid operators are +, -, , /. Division truncates toward zero.

Example

Input: tokens = ["2","1","+","3","*"]

Output: 9

Explanation: ((2 + 1) * 3) = 9.

Constraints

• 1 ≤ tokens.length ≤ 10⁴
• Each token is an operator (+, -, *, /) or an integer in [-200, 200]

Topics & Companies

Topics: stack, arrays

Asked by: Amazon, Google, LinkedIn

Optimal Solution Complexity

Time complexity: O(n). Space complexity: O(n).

Practice more

• All DSA Problems
• DSA Patterns