feat(work): add Course Schedule II solution and clean up Course Schedule I implementation

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Prad Nukala committed 2026-09-22 14:24:38 -04:00
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@@ -31,4 +31,26 @@ sidebar:
```py ```py
class Solution: class Solution:
def canFinish(self, numCourses: int, prerequisites: list[list[int]]) -> bool: def canFinish(self, numCourses: int, prerequisites: list[list[int]]) -> bool:
indegree = [0] * numCourses
adj = [[] for x in range(numCourses)]
for prereq in prerequisites:
adj[prereq[1]].append(prereq[0])
indegree[prereq[0]] += 1
queue = []
for i in range(numCourses):
if indegree[i] == 0:
queue.append(i)
visited = 0
while queue:
node = queue.pop(0)
visited += 1
for neighbor in adj[node]:
indegree[neighbor] -= 1
if indegree[neighbor] == 0:
queue.append(neighbor)
return numCourses == visited
``` ```
@@ -0,0 +1,39 @@
---
title: '210. Course Schedule II'
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
sidebar:
label: 'Course Schedule II'
badge: 'Medium'
---
<Badge variant="accent">Depth-First Search</Badge>
### Example 1:
- Input: `numCourses = 2, prerequisites = [[1,0]]`
- Output: `[0,1]`
- Explanation: There are a total of `2` courses to take. To take course `1` you should have finished course `0`. So the correct course order is `[0,1]`.
### Example 2:
- Input: `numCourses = 4, prerequisites = [[1,0],[2,0],[3,1],[3,2]]`
- Output: `[0,2,1,3]`
- Explanation: There are a total of `4` courses to take. To take course `3` you should have finished both courses `1` and `2`. Both courses `1` and `2` should be taken after you finished course `0`. So one correct course order is `[0,1,2,3]`. Another correct ordering is `[0,2,1,3]`.
### Example 3:
- Input: `numCourses = 1, prerequisites = []`
- Output: `[0]`
### Constraints:
- `1 <= numCourses <= 2000`
- `0 <= prerequisites.length <= numCourses * (numCourses - 1)`
- `prerequisites[i].length == 2`
- `0 <= ai, bi < numCourses`
- `ai != bi`
- All the pairs [ai, bi] are distinct.
## Solution
```py
class Solution:
def findOrder(self, numCourses: int, prerequisites: list[list[int]]) -> list[int]:
```
@@ -47,6 +47,28 @@ Constraints:
• All the pairs prerequisites[i] are unique. • All the pairs prerequisites[i] are unique.
""" """
class Solution: class Solution:
def canFinish(self, numCourses: int, prerequisites: list[list[int]]) -> bool: def canFinish(self, numCourses: int, prerequisites: list[list[int]]) -> bool:
indegree = [0] * numCourses
adj = [[] for x in range(numCourses)]
for prereq in prerequisites:
adj[prereq[1]].append(prereq[0])
indegree[prereq[0]] += 1
queue = []
for i in range(numCourses):
if indegree[i] == 0:
queue.append(i)
visited = 0
while queue:
node = queue.pop(0)
visited += 1
for neighbor in adj[node]:
indegree[neighbor] -= 1
if indegree[neighbor] == 0:
queue.append(neighbor)
return numCourses == visited
@@ -0,0 +1,64 @@
"""
210. Course Schedule II
Difficulty: Medium
https://leetcode.com/problems/course-schedule-ii/
──────────────────────────────────────────────────
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.
• For example, the pair [0, 1], indicates that to take course 0 you
have to first take course 1.
Return the ordering of courses you should take to finish all courses.
If there are many valid answers, return any of them. If it is
impossible to finish all courses, return an empty array.
Example 1:
Input: numCourses = 2, prerequisites = [[1,0]]
Output: [0,1]
Explanation: There are a total of 2 courses to take. To take course 1
you should have finished course 0. So the correct course order is
[0,1].
Example 2:
Input: numCourses = 4, prerequisites = [[1,0],[2,0],[3,1],[3,2]]
Output: [0,2,1,3]
Explanation: There are a total of 4 courses to take. To take course 3
you should have finished both courses 1 and 2. Both courses 1 and 2
should be taken after you finished course 0.
So one correct course order is [0,1,2,3]. Another correct ordering is
[0,2,1,3].
Example 3:
Input: numCourses = 1, prerequisites = []
Output: [0]
Constraints:
• 1 <= numCourses <= 2000
• 0 <= prerequisites.length <= numCourses * (numCourses - 1)
• prerequisites[i].length == 2
• 0 <= ai, bi < numCourses
• ai != bi
• All the pairs [ai, bi] are distinct.
"""
class Solution:
def findOrder(self, numCourses: int, prerequisites: list[list[int]]) -> list[int]: