Leetcode Problem 1136. Parallel Courses

1136. Parallel Courses

Leetcode Solutions

Build a directed graph from relations and record the in-degree of each node.
Initialize a queue and add all nodes with an in-degree of 0 to it.
Initialize step to 0 and visited_count to 0.
While the queue is not empty: a. Increment step. b. For each node in the queue, increment visited_count. c. For each neighbor of the node, decrement its in-degree. d. If a neighbor's in-degree reaches 0, add it to the next queue. e. Update the queue with the next queue.
If visited_count equals the total number of courses, return step. Otherwise, return -1.

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