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58 lines
1.8 KiB
Plaintext
58 lines
1.8 KiB
Plaintext
---
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title: '207. Course Schedule'
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description: There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, bi] indicates that you must take course bi first if you want to take course ai
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icon: dot
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sidebar:
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label: 'Course Schedule'
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badge: 'Medium'
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---
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<Badge variant="accent">Depth-First Search</Badge>
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### Example 1:
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- Input: `numCourses = 2, prerequisites = [[1,0]]`
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- Output: `true`
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- Explanation: There are a total of `2` courses to take. To take course `1` you should have finished course `0`. So it is possible.
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### Example 2:
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- Input: `numCourses = 2, prerequisites = [[1,0],[0,1]]`
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- Output: `false`
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- Explanation: There are a total of `2` courses to take. To take course `1` you should have finished course `0`, and to take course `0` you should also have finished course `1`. So it is impossible.
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### Constraints:
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- `1 <= numCourses <= 2000`
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- `0 <= prerequisites.length <= 5000`
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- `prerequisites[i].length == 2`
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- `0 <= ai, bi < numCourses`
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- All the pairs `prerequisites[i]` are unique.
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## Solution
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```py
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class Solution:
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def canFinish(self, numCourses: int, prerequisites: list[list[int]]) -> bool:
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indegree = [0] * numCourses
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adj = [[] for x in range(numCourses)]
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for prereq in prerequisites:
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adj[prereq[1]].append(prereq[0])
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indegree[prereq[0]] += 1
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queue = []
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for i in range(numCourses):
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if indegree[i] == 0:
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queue.append(i)
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visited = 0
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while queue:
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node = queue.pop(0)
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visited += 1
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for neighbor in adj[node]:
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indegree[neighbor] -= 1
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if indegree[neighbor] == 0:
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queue.append(neighbor)
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return numCourses == visited
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```
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