feat: 207. Course Schedule

Author: gwbaik9717

course-schedule/gwbaik9717.js

@@ -0,0 +1,68 @@
+// n: numCourses, p: len(prerequisites)
+// Time complexity: O(n + p)
+// Space complexity: O(n + p)
+
+class _Queue {
+  constructor() {
+    this.q = [];
+    this.start = 0;
+    this.end = 0;
+  }
+
+  isEmpty() {
+    return this.start === this.end;
+  }
+
+  push(value) {
+    this.q.push(value);
+    this.end++;
+  }
+
+  shift() {
+    const rv = this.q[this.start];
+    delete this.q[this.start++];
+
+    return rv;
+  }
+}
+
+/**
+ * @param {number} numCourses
+ * @param {number[][]} prerequisites
+ * @return {boolean}
+ */
+var canFinish = function (numCourses, prerequisites) {
+  const graph = Array.from({ length: numCourses }, () => []);
+  const inDegree = Array.from({ length: numCourses }, () => 0);
+
+  for (const [end, start] of prerequisites) {
+    graph[start].push(end);
+    inDegree[end]++;
+  }
+
+  const q = new _Queue();
+
+  for (let i = 0; i < numCourses; i++) {
+    if (inDegree[i] === 0) {
+      q.push(i);
+    }
+  }
+
+  let count = 0;
+
+  while (!q.isEmpty()) {
+    const current = q.shift();
+    count++;
+
+    // 현재 노드와 연결된 다른 노드의 차수 감소
+    for (const node of graph[current]) {
+      inDegree[node] -= 1;
+
+      if (inDegree[node] === 0) {
+        q.push(node);
+      }
+    }
+  }
+
+  return count === numCourses;
+};