✨ [207] Course Schedule - topological sort

Author: enkr1

207/my_solution.js

@@ -0,0 +1,55 @@
+/**
+ * @param {number} numCourses
+ * @param {number[][]} prerequisites
+ * @return {boolean}
+ */
+const canFinish = function (numCourses, prerequisites) {
+  // Step 1: Build the graph (adjacency list)
+  // console.log(graph)
+  const graph = buildGraph(numCourses, prerequisites);
+  console.log("graph (adjacency list)")
+  console.log(graph)
+
+  // Step 2: Perform topological sort
+  const inDegree = new Array(numCourses).fill(0);
+  for (let [course, pre] of prerequisites) {
+    inDegree[course]++;
+  }
+  console.log("inDegree")
+  console.log(inDegree)
+
+  const queue = [];
+  for (let i = 0; i < numCourses; i++) {
+    if (inDegree[i] === 0) {
+      queue.push(i);
+    }
+  }
+
+  let count = 0;
+  while (queue.length > 0) {
+    const course = queue.shift();
+    count++;
+
+    for (const neighbor of graph[course]) {
+      inDegree[neighbor]--;
+      if (inDegree[neighbor] === 0) {
+        queue.push(neighbor);
+      }
+    }
+  }
+
+  // Step 3: Check the count
+  return count === numCourses;
+};
+
+// Helper function to build the graph
+function buildGraph(numCourses, prerequisites) {
+  const graph = new Array(numCourses).fill().map(() => []);
+  for (const [course, prerequisite] of prerequisites) {
+    graph[prerequisite].push(course);
+  }
+  return graph;
+}
+
+console.log(canFinish(2, [[1, 0]])); // Output: true
+console.log(canFinish(2, [[1, 0], [0, 1]])); // Output: false

207/solution.js

@@ -0,0 +1,50 @@
+/**
+ * @param {number} numCourses
+ * @param {number[][]} prerequisites
+ * @return {boolean}
+ */
+const canFinish = function (numCourses, prerequisites) {
+  // Step 1: Build the graph (adjacency list)
+  const graph = buildGraph(numCourses, prerequisites);
+
+  // Step 2: Perform topological sort
+  const inDegree = new Array(numCourses).fill(0);
+  for (let [course, pre] of prerequisites) {
+    inDegree[course]++;
+  }
+
+  const queue = [];
+  for (let i = 0; i < numCourses; i++) {
+    if (inDegree[i] === 0) {
+      queue.push(i);
+    }
+  }
+
+  let count = 0;
+  while (queue.length > 0) {
+    const course = queue.shift();
+    count++;
+
+    for (const neighbor of graph[course]) {
+      inDegree[neighbor]--;
+      if (inDegree[neighbor] === 0) {
+        queue.push(neighbor);
+      }
+    }
+  }
+
+  // Step 3: Check the count
+  return count === numCourses;
+};
+
+// Helper function to build the graph
+function buildGraph(numCourses, prerequisites) {
+  const graph = new Array(numCourses).fill().map(() => []);
+  for (const [course, prerequisite] of prerequisites) {
+    graph[prerequisite].push(course);
+  }
+  return graph;
+}
+
+console.log(canFinish(2, [[1, 0]])); // Output: true
+console.log(canFinish(2, [[1, 0], [0, 1]])); // Output: false

README.md

@@ -43,6 +43,7 @@
 - [198. House Robber](./198/)
 - [200. Number of Islands](./200/)
 - [206. Reverse Linked List](./206/)
+- [207. Course Schedule](./207/)
 - [213. House Robber II](./213/)
 - [217. Contains Duplicate](./217/)
 - [238. Product of Array Except Self](./238/)
@@ -105,7 +106,7 @@ Batch create:
 NOTE: JS IS HERE
 -->
 ```ssh
-chapter=435 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
+chapter=207 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
 ```
 > then you can use `x` for quick debug.
 

test.js

@@ -55,3 +55,6 @@ console.log(o)
 let x = Array(3).fill([]);
 x[1].push(2)
 console.log(x)
+
+const g = Array(3).fill().map(() => []);
+console.log(g)