void dfs(string str, int level, int removeLevel, int cnt, pair<char, char> par) {
    if (level == str.length()) {
        string temp = str;
        reverse(temp.begin(), temp.end());
        if (par.first == '(') {
            dfs(temp, 0, 0, 0, {')', '('});
        } else {
            results.push_back(temp);
        }
        return;
    }

    if (str[level] == par.first) {
        dfs(str, level + 1, removeLevel, cnt + 1, par);
    } else if (str[level] == par.second) {
        cnt--;

        if (cnt < 0) {
            for (int j = removeLevel; j <= level; j++) {
                if (str[j] == par.second && (j == removeLevel || str[j - 1] != par.second)) {
                    dfs(str.substr(0, j) + str.substr(j + 1), level, j, 0, par);
                }
            }
        } else {
            dfs(str, level + 1, removeLevel, cnt, par);
        }
    } else {
        dfs(str, level + 1, removeLevel, cnt, par);
    }
}

vector<string> results;
vector<string> removeInvalidParentheses(string str) {
    dfs(str, 0, 0, 0, {'(', ')'});
    return results;
}