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Evaluate Reverse Polish Notation (medium)
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Problem Statement

Given an array of strings tokens that represents an arithmetic expression in Reverse Polish Notation (RPN), evaluate the expression and return the resulting integer value.

  • The valid operators are '+', '-', '*', and '/'.
  • Each operand can be an integer or another expression.
  • Division between two integers should truncate towards zero.
  • No division by zero will occur.
  • The input is a valid RPN expression.
  • All results fit within a 32-bit integer.

Examples

Example 1

  • Input: tokens = ["2", "11", "5", "/", "+"]
  • Output: 4
  • Explanation: (11 / 5) = 2, then (2 + 2) = 4.

Example 2

  • Input: tokens = ["2", "3", "11", "+", "*"]
  • Output: 28
  • Explanation: (11 + 3) = 14, then (2 * 14) = 28.

Example 3

  • Input: tokens = ["5", "1", "2", "+", "4", "*", "+", "3", "-"]
  • Output: 14
  • Explanation: (1 + 2) = 3, (3 * 4) = 12, (5 + 12) = 17, (17 - 3) = 14.

Constraints:

  • 1 <= tokens.length <= 10<sup>4</sup>
  • tokens[i] is either an operator: "+", "-", "*", or "/", or an integer in the range [-200, 200].

Try it yourself

Try solving this question here:

Python3
Python3
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