public class Solution
extends Object
301 - Remove Invalid Parentheses\.
Hard
Given a string `s` that contains parentheses and letters, remove the minimum number of invalid parentheses to make the input string valid.
Return _all the possible results_. 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:** [""]
**Constraints:**
* `1 <= s.length <= 25`
* `s` consists of lowercase English letters and parentheses `'('` and `')'`.
* There will be at most `20` parentheses in `s`.