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course_schedule.js
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course_schedule.js
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//given a integer n representing the number of courses, and a 2D array of integers representing the prerequisites,
//determines if it is possible to take all courses.
//prerequisites[i][0] is the course that must be taken before taking prerequisites[i][1]
//we have check to check if there exists a cycle in the graph
const courseSchedule = (n, prerequisites) => {
let graph = new Map();
let id = new Array(n).fill(0);
let q = [];
let result = true;
for (let i = 0; i < prerequisites.length; i++) {
let [course, prerequisite] = prerequisites[i];
if (!graph.has(course)) {
graph.set(course, []);
}
graph.get(course).push(prerequisite);
id[prerequisite]++;
}
for (let i = 0; i < id.length; i++) {
if (id[i] === 0) {
q.push(i);
}
}
while (q.length > 0) {
let course = q.shift();
for (let i = 0; i < graph.get(course)?.length; i++) {
let prerequisite = graph.get(course)[i];
id[prerequisite]--;
if (id[prerequisite] === 0) {
q.push(prerequisite);
}
}
}
for (let i = 0; i < id.length; i++) {
if (id[i] !== 0) {
result = false;
break;
}
}
return result;
}
let n = 6;
let prerequisites = [[3, 0], [1, 3], [2, 1], [4, 1], [4, 2], [5, 3], [5, 4]];
console.log(courseSchedule(n, prerequisites));