课程表与依赖环检测

/*
 * 题目：课程表与依赖环检测
 * 要求：输入非负整数 numCourses（课程编号 0 到 numCourses-1）和先修关系数组 prerequisites；每项 [course, prerequisite] 的编号均有效，表示先学 prerequisite 才能学 course。返回一种包含全部课程且满足依赖的顺序；有环时返回 []，重复关系视为一条边，零门课程返回 []。
 * 示例：numCourses=3、prerequisites=[[1,0],[2,1]] 返回 [0,1,2]；[[1,0],[0,1]] 形成环，返回 []。
 */
function findCourseOrder(numCourses, prerequisites) {}
console.log(findCourseOrder(2, [[1, 0]])); // 预期：[0, 1]
console.log(findCourseOrder(2, [[1, 0], [0, 1]])); // 预期：[]
console.log(findCourseOrder(3, [[1, 0], [1, 0], [2, 1]])); // 预期：[0, 1, 2]
console.log(findCourseOrder(0, [])); // 预期：[]

function findCourseOrder(numCourses, prerequisites) {
  if (!Number.isInteger(numCourses) || numCourses < 0)
    throw new RangeError("invalid numCourses");
  const graph = Array.from({ length: numCourses }, () => []);
  const indegree = Array(numCourses).fill(0);
  const edges = new Set();
  for (const pair of prerequisites) {
    if (!Array.isArray(pair) || pair.length !== 2)
      throw new TypeError("invalid prerequisite");
    const [course, prerequisite] = pair;
    if (
      ![course, prerequisite].every(
        (v) => Number.isInteger(v) && v >= 0 && v < numCourses,
      )
    )
      throw new RangeError("course out of range");
    const key = `${prerequisite}:${course}`;
    if (edges.has(key)) continue;
    edges.add(key);
    graph[prerequisite].push(course);
    indegree[course] += 1;
  }
  const queue = [];
  for (let i = 0; i < numCourses; i += 1) if (indegree[i] === 0) queue.push(i);
  const order = [];
  for (let head = 0; head < queue.length; head += 1) {
    const course = queue[head];
    order.push(course);
    for (const next of graph[course]) {
      indegree[next] -= 1;
      if (indegree[next] === 0) queue.push(next);
    }
  }
  return order.length === numCourses ? order : [];
}

// 三组以上可直接运行的验证。
console.log(findCourseOrder(2, [[1, 0]])); // 预期：[0, 1]
console.log(findCourseOrder(2, [[1, 0], [0, 1]])); // 预期：[]
console.log(findCourseOrder(3, [[1, 0], [1, 0], [2, 1]])); // 预期：[0, 1, 2]
console.log(findCourseOrder(0, [])); // 预期：[]