Merge pull request #2446 from t3chkid/main

add Kotlin solution for 1462. Course Schedule IV

Author: a93a

Diff for: kotlin/1462-course-schedule-iv.kt

@@ -0,0 +1,34 @@
+class Solution {
+    fun checkIfPrerequisite(
+        numCourses: Int,
+        prerequisites: Array<IntArray>,
+        queries: Array<IntArray>
+    ): List<Boolean> {
+        // { course -> [ immediate pre-requisites ] }
+        val adjacencyList = mutableMapOf<Int, MutableList<Int>>()
+        prerequisites.forEach { (immediatePrerequisite, course) ->
+            adjacencyList.getOrPut(course) { mutableListOf() }.add(immediatePrerequisite)
+        }
+        // { course -> [ complete set of prerequisites including transitive pre-requisites ] }
+        val prerequisitesMap = mutableMapOf<Int, HashSet<Int>>()
+        fun dfs(startCourse: Int, currentCourse: Int = startCourse) {
+            if (currentCourse in (prerequisitesMap[startCourse] ?: hashSetOf())) return
+            if (currentCourse != startCourse) {
+                prerequisitesMap.getOrPut(startCourse) { hashSetOf() }.add(currentCourse)
+            }
+            for (immediatePrerequisite in adjacencyList[currentCourse] ?: mutableListOf()) {
+                dfs(startCourse, immediatePrerequisite)
+            }
+        }
+
+        for (course in 0 until numCourses) {
+            dfs(startCourse = course)
+        }
+
+        val resultantList = mutableListOf<Boolean>()
+        queries.forEach { (prerequisite, course) ->
+            resultantList.add(prerequisitesMap[course]?.let { prerequisite in it } ?: false)
+        }
+        return resultantList
+    }
+}