Array ( [0] => Array ( [title] => L21A [link] => https://www.youtube.com/embed/dtodbCAG3gU ) [1] => Array ( [title] => L21B [link] => https://www.youtube.com/embed/_K17bJZG3yg ) ) 國立清華大學開放式課程OpenCourseWare(NTHU, OCW) - 第21講 Subset & Set Operations_Union, Intersection, Complement