Leetcode Problem 772. Basic Calculator III

772. Basic Calculator III

Leetcode Solutions

Key approach of the solution: Stack-based Evaluation with Parentheses Handling

  1. Initialize a stack to store terms and operators.
  2. Initialize curr to track the current number being built and previousOperator to track the last operator seen.
  3. Iterate over the input expression character by character.
  4. If the character is a digit, update curr to include the digit.
  5. If the character is an operator or a parenthesis, process the current term based on previousOperator and push the result onto the stack.
  6. If an open parenthesis ( is encountered, push previousOperator onto the stack and reset curr and previousOperator for the new isolated expression.
  7. If a closing parenthesis ) is encountered, pop and sum all terms until an operator is reached, then use this operator to process the result of the isolated expression.
  8. After the iteration, sum all terms in the stack to get the final result.
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Key approach of the solution: Recursive Evaluation of Nested Expressions

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