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Solution: Remove Invalid Parentheses

Explore how to solve the problem of removing invalid parentheses from a string by applying recursive backtracking. Learn to identify the minimum removals needed and generate all unique valid strings with balanced parentheses, applying core backtracking concepts for algorithmic problem solving.

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 ...