0210-course-schedule-ii.java

classSolution {

publicint[] findOrder(intnumCourses, int[][] prerequisites) {
Map<Integer, List<Integer>> adjList = newHashMap<Integer, List<Integer>>();
int[] indegree = newint[numCourses];
int[] topologicalOrder = newint[numCourses];

//creating the adjlist
for (inti = 0; i < prerequisites.length; i++) {
intpost = prerequisites[i][0];
intpre = prerequisites[i][1];
List<Integer> lst = adjList.getOrDefault(
pre,
newArrayList<Integer>()
 );
lst.add(post);
adjList.put(pre, lst);

indegree[post] += 1;
 }

Queue<Integer> q = newLinkedList<Integer>();
for (inti = 0; i < numCourses; i++) {
if (indegree[i] == 0) {
q.add(i);
 }
 }

inti = 0;
while (!q.isEmpty()) {
intnode = q.remove();
topologicalOrder[i++] = node;

if (adjList.containsKey(node)) {
for (Integerneighbor : adjList.get(node)) {
indegree[neighbor]--;

if (indegree[neighbor] == 0) {
q.add(neighbor);
 }
 }
 }
 }

if (i == numCourses) {
returntopologicalOrder;
 }

returnnewint[0];
 }
}