Algorithm Notes
Summary: Course Schedule Ii — notes not yet curated.
Time: Estimate via loops/recurrences; common classes: O(1), O(log n), O(n), O(n log n), O(n^2)
Space: Count auxiliary structures and recursion depth.
Tip: See the Big-O Guide for how to derive bounds and compare trade-offs.
Big-O Guide
Source
"""
Course Schedule Ii
TODO: Add problem description
"""
from collections import defaultdict, deque
from src.interview_workbook.leetcode._registry import register_problem
from src.interview_workbook.leetcode._types import Category, Difficulty
class Solution:
def solve(self, numCourses, prerequisites):
"""Topological sort: return valid order of courses or [] if impossible."""
graph = defaultdict(list)
indegree = [0] * numCourses
for dest, src in prerequisites:
graph[src].append(dest)
indegree[dest] += 1
queue = deque([i for i in range(numCourses) if indegree[i] == 0])
order = []
while queue:
course = queue.popleft()
order.append(course)
for nei in graph[course]:
indegree[nei] -= 1
if indegree[nei] == 0:
queue.append(nei)
return order if len(order) == numCourses else []
def demo():
"""Run a demo for the Course Schedule II problem."""
solver = Solution()
numCourses = 4
prerequisites = [[1, 0], [2, 0], [3, 1], [3, 2]]
result = solver.solve(numCourses, prerequisites)
return str(result)
register_problem(
id=210,
slug="course_schedule_ii",
title="Course Schedule II",
category=Category.GRAPHS,
difficulty=Difficulty.MEDIUM,
tags=["dfs", "bfs", "graph", "topological_sort"],
url="https://leetcode.com/problems/course-schedule-ii/",
notes="",
)