Update 207-course-schedule.js

Author: everthis

207-course-schedule.js

@@ -72,3 +72,40 @@ const canFinish = function(vertices, edges) {
   }
   return sortedOrder.length === vertices ? true : false
 }
+
+// another
+
+/**
+ * @param {number} numCourses
+ * @param {number[][]} prerequisites
+ * @return {boolean}
+ */
+const canFinish = function(numCourses, prerequisites) {
+  const set = new Set(), hash = {}
+  for(let i = 0; i < prerequisites.length; i++) {
+    const [cur, pre] = prerequisites[i]
+    if(hash[cur] == null) hash[cur] = new Set()
+    hash[cur].add(pre)
+  }
+  const q = []
+
+  for(let i = 0; i < numCourses; i++) {
+    if(hash[i] == null) q.push(i)
+  }
+  let visited = 0
+
+  while(q.length) {
+    const cur = q.shift()
+    visited++
+    Object.keys(hash).forEach(k => {
+       if(hash[k].has(cur)) {
+         hash[k].delete(cur)
+       }
+       if(hash[k].size === 0) {
+         delete hash[k]
+         q.push(+k)
+       }
+    })
+  }
+  return visited === numCourses
+};