Evaluate Reverse Polish Notation Medium 0 attempts
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Evaluate Reverse Polish Notation

Medium Stack&Queue LeetCode

Evaluate an expression in Reverse Polish Notation. Valid operators are +, -, *, /. Division truncates toward zero.

Example: tokens = ["2","1","+","3","*"] → Output: 9 ((2+1)*3)

Sample Input
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Sample Output
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Constraints
  • 1 <= tokens.length <= 10^4
  • tokens[i] is an operator or integer in [-200, 200]
Test Cases
Case 1
Args: [["2","1","+","3","*"]] Expected: 9
Case 2
Args: [["4","13","5","/","+"]] Expected: 6
Topics
Stack&Queue

Stack

function evalRPN(tokens) {
  const stack = [];
  for (const t of tokens) {
    if ('+-*/'.includes(t)) {
      const b = stack.pop(), a = stack.pop();
      if (t === '+') stack.push(a + b);
      else if (t === '-') stack.push(a - b);
      else if (t === '*') stack.push(a * b);
      else stack.push(Math.trunc(a / b));
    } else stack.push(Number(t));
  }
  return stack[0];
}

Time: O(n) | Space: O(n)

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