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Medium
Evaluate Reverse Polish Notation
#62stackarraymath
Use stack: push numbers, pop two operands on operator, compute and push result.
Example:
Input:
tokens=['2','1','+','3','*']Output:
9 ((2+1)*3)Common Mistakes:
- Wrong operand order (a = second pop, b = first pop, compute a op b)
- Not handling negative numbers in input
- Using switch without break statements
- Forgetting division truncates toward zero
Notes:
Classic stack application. Time O(n), Space O(n). RPN avoids parentheses and operator precedence issues.
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Use stack: push numbers, pop two operands on operator, compute and push result.
Example:
Input:
tokens=['2','1','+','3','*']Output:
9 ((2+1)*3)Common Mistakes:
- Wrong operand order (a = second pop, b = first pop, compute a op b)
- Not handling negative numbers in input
- Using switch without break statements
- Forgetting division truncates toward zero
Notes:
Classic stack application. Time O(n), Space O(n). RPN avoids parentheses and operator precedence issues.
62/75
Evaluate Reverse Polish Notation