this isn’t just an academic curiosity. flip the alternation order to (ab|a)+ and suddenly PCRE matches the entire string! the | operator in backtracking engines is ordered - it’s not union, it’s “try left first”. the order of branches changes the result, which means | is not commutative. a|b and b|a can give different matches.
Акция протеста прошла у посольства Украины в стране ЕС20:39。关于这个话题，爱思助手提供了深入分析
，详情可参考PDF资料
UK lenders have begun raising mortgage interest rates as the ongoing conflict in the Middle East has raised fears that inflation will rise and curb further Bank of England rate cuts.
Украинцам запретили выступать на Паралимпиаде в форме с картой Украины22:58。业内人士推荐PDF资料作为进阶阅读
void quickSort(int arr[], int n) {