Hard
Quiz
#301 Remove Invalid Parentheses
APPROACH
Given a string s that contains parentheses and letters, remove the minimum number of invalid parentheses to make the input string valid.
Return a list of unique strings that are valid with the minimum number of removals. You may return the answer in any order.
Example 1:
Input: s = "()())()"
Output: ["(())()","()()()"]
Example 2:
Input: s = "(a)())()"
Output: ["(a())()","(a)()()"]
Example 3:
Input: s = ")("
Output: [""]
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What is the optimal approach for this problem?