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Solution: Remove Invalid Parentheses

Explore the backtracking method to solve the problem of removing the minimum number of invalid parentheses from a string. Understand how to track unmatched parentheses, recurse through all possible combinations, and ensure valid balanced expressions are generated. This lesson helps you implement and analyze the time and space complexity of this approach.

Statement

You are given a string, s, that contains:

  • Lowercase English letters

  • Opening '(' and closing ')' parentheses

A string is considered valid if:

  1. All opening parentheses '(' are closed properly by a matching ')'.

  2. The parentheses are in the correct order and nesting.

  3. Letters can appear anywhere and do not affect validity.

Return all possible valid strings that can be formed by removing the minimum number of invalid parentheses. The answer must be a list of unique strings, in any order.

Constraints:

  • 1 ...