Check if you can finish every course when some need to be done first. We build the course graph, run Kahn\u2019s BFS topological sort, and detect cycles. Step-by-step intuition, detailed code explanation, dry run, and Big-O analysis.<\/p>\n\n\n\n
Here’s the [Problem Link<\/span><\/mark><\/a><\/strong>] to begin with.<\/p>\n\n\n You have Take course Return 1. What does the problem ask?<\/h2>\n\n\n\n
numCourses<\/code> labeled 0 \u2026 numCourses \u2212 1<\/code>.
Each pair [a, b]<\/code> in prerequisites<\/code> means:<\/p>\n\n\n\n\n
b<\/code> before course a<\/code>.<\/strong><\/p>\n<\/blockquote>\n\n\n\nTrue<\/code><\/strong> if you can take all courses in some order.
Return False<\/code><\/strong> if the rules create a cycle that blocks progress.<\/p>\n\n\n\n
\n\n\n\n2. Quick examples<\/h2>\n\n\n\n
numCourses<\/code><\/th>prerequisites<\/code><\/th>Result<\/th> Why<\/th><\/tr><\/thead> 2<\/code><\/td>[[1, 0]]<\/code><\/td>True<\/code><\/td>Take 0<\/strong> \u279c then 1<\/strong>.<\/td><\/tr> 2<\/code><\/td>[[1, 0], [0, 1]]<\/code><\/td>False<\/code><\/td>0 needs 1 and 1 needs 0 \u2192 cycle.<\/td><\/tr> 4<\/code><\/td>[[1,0],[2,0],[3,1],[3,2]]<\/code><\/td>True<\/code><\/td>0 \u279c (1,2) \u279c 3.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n \n