301. Remove Invalid Parentheses

题目

Remove the minimum number of invalid parentheses in order to make the input string valid. Return all possible results.

Note: The input string may contain letters other than the parentheses ( and ).

Examples:

"()())()" -> ["()()()", "(())()"]
"(a)())()" -> ["(a)()()", "(a())()"]
")(" -> [""]

Credits:Special thanks to @hpplayer for adding this problem and creating all test cases.

解题思路

见程序注释