Grokking Data Structures & Algorithms for Coding Interviews
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Solution: Evaluate Reverse Polish Notation

Problem Statement

Evaluate an arithmetic expression given in Reverse Polish Notation and return the integer result. Division truncates toward zero.

Examples

Example 1

  • Input: tokens = ["2", "1", "+", "3", "*"]
  • Expected Output: 9

Example 2

  • Input: tokens = ["4", "13", "5", "/", "+"]
  • Expected Output: 6

Example 3

  • Input: tokens = ["3", "-4", "*"]
  • Expected Output: -12

Why this is a stack problem

Reverse Polish Notation puts the operator after its two values, which is exactly why it needs no brackets

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