std::regex 是否保证了最坏情况下的时间复杂度?

它似乎确实考虑了时间复杂度，但我怀疑它是否基于任何理论上的最坏或最佳情况假设; 它应该可能基于一些相对超过一定时间量的权衡，这里称为pre-set level：

/** * 尝试与常规比赛的复杂性 表达式超出预设水平。 */

参考

/** The expression contained an invalid collating element name. */
constexpr error_type error_collate(_S_error_collate);
/** The expression contained an invalid character class name. */
constexpr error_type error_ctype(_S_error_ctype);
/**
* The expression contained an invalid escaped character, or a trailing
* escape.
*/
constexpr error_type error_escape(_S_error_escape);
/** The expression contained an invalid back reference. */
constexpr error_type error_backref(_S_error_backref);
/** The expression contained mismatched [ and ]. */
constexpr error_type error_brack(_S_error_brack);
/** The expression contained mismatched ( and ). */
constexpr error_type error_paren(_S_error_paren);
/** The expression contained mismatched { and } */
constexpr error_type error_brace(_S_error_brace);
/** The expression contained an invalid range in a {} expression. */
constexpr error_type error_badbrace(_S_error_badbrace);
/**
* The expression contained an invalid character range,
* such as [b-a] in most encodings.
*/
constexpr error_type error_range(_S_error_range);
/**
* There was insufficient memory to convert the expression into a
* finite state machine.
*/
constexpr error_type error_space(_S_error_space);
/**
* One of <em>*?+{</em> was not preceded by a valid regular expression.
*/
constexpr error_type error_badrepeat(_S_error_badrepeat);
/**
* The complexity of an attempted match against a regular expression
* exceeded a pre-set level.
*/
constexpr error_type error_complexity(_S_error_complexity);
/**
* There was insufficient memory to determine whether the
* regular expression could match the specified character sequence.
*/
constexpr error_type error_stack(_S_error_stack);