Remove Invalid Parentheses

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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())()"]")(" -> [""]class Solution {public:    vector<string> removeInvalidParentheses(string s) {        set<string> temp;        int n = s.length();        int left_remove = 0;        int right_remove = 0;        for (int i = 0; i < n; i++)        {            if (s[i] == '(')            {                left_remove++;            }            else if (s[i] == ')')            {                if (left_remove > 0)                {                    left_remove--;                }                else                {                    right_remove++;                }            }        }        visit(s, n, 0, left_remove, right_remove, 0, 0, "", temp);        vector<string> result(temp.begin(), temp.end());        return result;    }private:    void visit(string &s, int n, int pos, int left_remove, int right_remove,            int left_count, int right_count, string buf, set<string> &temp)    {        if (n == pos)        {            if (left_remove == 0 && right_remove == 0)            {                temp.insert(buf);            }            return;        }        if (s[pos] == '(')        {            if (left_remove > 0)            {                visit(s, n, pos+1, left_remove-1, right_remove, left_count, right_count, buf, temp);            }            visit(s, n, pos+1, left_remove, right_remove, left_count+1, right_count, buf+s[pos], temp);        }        else if (s[pos] == ')')        {            if (right_remove > 0)            {                visit(s, n, pos+1, left_remove, right_remove-1, left_count, right_count, buf, temp);            }            if (left_count <= right_count)            {                return;            }            visit(s, n, pos+1, left_remove, right_remove, left_count, right_count+1, buf+s[pos], temp);        }        else        {            visit(s, n, pos+1, left_remove, right_remove, left_count, right_count, buf+s[pos], temp);        }    }};

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