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JavaScript

1class Solution {

2 canFinish(numCourses, prerequisites) {

3 const graph = Array.from({ length: numCourses }, () => []);

4 const inDegree = Array(numCourses).fill(0);

6 for (const [course, prereq] of prerequisites) {

7 graph[prereq].push(course);

8 inDegree[course] += 1;

9 }

11 const queue = [];

12 for (let i = 0; i < numCourses; i += 1) {

13 if (inDegree[i] === 0) {

14 queue.push(i);

15 }

16 }

18 let completed = 0;

19 while (queue.length > 0) {

20 const course = queue.shift();

21 completed += 1;

23 for (const nextCourse of graph[course]) {

24 inDegree[nextCourse] -= 1;

25 if (inDegree[nextCourse] === 0) {

26 queue.push(nextCourse);

27 }

28 }

29 }

31 return completed === numCourses;

32 }

33}

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Topological Sort

Trees & Graphs

Laying out graph...

current

highlighted

queue

Only course 0 starts with in-degree 0, so the queue begins with [0].

02Figure it out yourself

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Predict

How much does each pass cost, and how many passes run?

A pass takes at most one course, then re-scans the rest from scratch.

03Prove it under pressure

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Sliding Window · hard

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Graph BFS · hard

Company signals

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Leaderboard Tracker

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