feat: osijvrsoi

pkg/questions/course_schedule/main.go

@@ -0,0 +1,53 @@
+package courseschedule
+
+func visit(prereqs map[int][]int, temporary map[int]bool, permanent map[int]bool, class int) bool {
+	if temporary[class] {
+		return false
+	}
+	if permanent[class] {
+		return true
+	}
+
+	if _, ok := prereqs[class]; !ok {
+		return true
+	}
+
+	temporary[class] = true
+
+	for _, p := range prereqs[class] {
+		if !visit(prereqs, temporary, permanent, p) {
+			return false
+		}
+	}
+
+	permanent[class] = true
+	temporary[class] = false
+
+	return true
+}
+
+func canFinish(numCourses int, prerequisites [][]int) bool {
+	prereqs := map[int][]int{}
+	for _, p := range prerequisites {
+		class, prerequisite := p[0], p[1]
+
+		if _, ok := prereqs[class]; !ok {
+			prereqs[class] = []int{}
+		}
+
+		prereqs[class] = append(prereqs[class], prerequisite)
+	}
+
+	temporary, permanent := map[int]bool{}, map[int]bool{}
+	for c := range prereqs {
+		if permanent[c] {
+			continue
+		}
+
+		if !visit(prereqs, temporary, permanent, c) {
+			return false
+		}
+	}
+
+	return true
+}