[leet] course schedules

Author: hyeonbinHur

허현빈/10주차/course schedule.js

@@ -0,0 +1,44 @@
+/**
+ * @param {number} numCourses
+ * @param {number[][]} prerequisites
+ * @return {boolean}
+ */
+var canFinish = function(numCourses, prerequisites) {
+    const from = new Map()
+    const to = new Map()
+    for(let i = 0 ; i < numCourses; i++){
+        from.set(i,0)
+    }
+
+    for(let i = 0 ; i < prerequisites.length; i++){
+        const [a,b] = prerequisites[i]
+        if(!to.get(b)) to.set(b, [])
+        to.get(b).push(a)
+        from.set(a, from.get(a)+1)
+    }
+
+    const q = []
+    for(let val of from){   
+        if(val[1] === 0){
+            q.push(val[0])
+            from.delete(val[0])
+        }
+    }
+    while(q.length){
+        const cur = q.shift()
+        const arr = to.get(cur)
+        if(arr){
+for(let i = 0 ; i < arr.length; i++ ){
+            const val  = to.get(cur)[i]
+            from.set(val, from.get(val) -1)
+            if(from.get(val) === 0){
+                q.push(val)
+                from.delete(val)
+            }
+        }
+        }
+        
+    }
+
+   return from.size ===0
+};

허현빈/10주차/course schedules2.js

@@ -0,0 +1,45 @@
+/**
+ * @param {number} numCourses
+ * @param {number[][]} prerequisites
+ * @return {number[]}
+ */
+var findOrder = function(numCourses, prerequisites) {
+    const from = new Map()
+    const to = new Map()
+    const ans =[]
+    for(let i = 0 ; i < numCourses; i++){
+        from.set(i, 0)
+    }
+    for(let i = 0 ; i < prerequisites.length; i++){
+        const [a,b] = prerequisites[i]
+        if(!to.get(b)) to.set(b, []) 
+        to.get(b).push(a)
+        from.set(a, from.get(a) + 1)
+    }
+    const q= []
+    
+    for(const val of from){
+        if(val[1] === 0){
+            q.push(val[0])
+            from.delete(val[0])
+        }
+    }
+
+    while(q.length){
+        const val = q.shift()
+        ans.push(val)
+        const arr = to.get(val)
+        if(arr) {
+             for(let i = 0 ; i < arr.length; i++){
+            const value = arr[i]
+            from.set(value, from.get(value)-1)
+            if(from.get(value) === 0){
+                q.push(value)
+                from.delete(value)
+            }
+        }
+        }
+       
+    }
+    return from.size === 0 ? ans : []
+};