#207

Course Schedule

medium· Graphsruns: 0

There are numCourses courses labeled 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [a, b] indicates that you must take course b before course a. Return true if it is possible to finish all courses.

wpm 0acc 100%time 0:000 / 780

class Solution:
    def canFinish(
        self, numCourses: int, prerequisites: list[list[int]]
    ) -> bool:
        graph = {i: [] for i in range(numCourses)}
        for course, pre in prerequisites:
            graph[course].append(pre)
        visited = set()

        def dfs(course: int) -> bool:
            if course in visited:
                return False
            if not graph[course]:
                return True
            visited.add(course)
            for pre in graph[course]:
                if not dfs(pre):
                    return False
            visited.remove(course)
            graph[course] = []
            return True

        for course in range(numCourses):
            if not dfs(course):
                return False
        return True

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