Course Schedule II

class Solution {
  int[] res;
	int resIdx = 0;
	boolean[] visited;
	List<List<Integer>> adjacencyList;
	public int[] findOrder(int numCourses, int[][] prerequisites) {
		res = new int[numCourses];
		visited = new boolean[numCourses];
		adjacencyList = createAdjacencyList(numCourses, prerequisites);
		Stack<Integer> visitesInDfs = new Stack<>();
		for (int i = 0; i < numCourses; i++) {
			if (!dfs(i, visitesInDfs)) {
				int[] tmpRes = {};
				return tmpRes;
			}
		}
		return res;
	}


	public boolean dfs(int currCourseNum, Stack<Integer> visitesInDfs) {
		if (visitesInDfs.contains(currCourseNum)) {
			return false;
		}
		if (visited[currCourseNum]) {
			return true;
		}
		visited[currCourseNum] = true;
		visitesInDfs.add(currCourseNum);
		List<Integer> currCourseWithPreq = adjacencyList.get(currCourseNum);
		for (int preq : currCourseWithPreq) {
			if (!dfs(preq, visitesInDfs)) {
				return false;
			}
		}
		res[resIdx++] = currCourseNum;
		visitesInDfs.pop();
		return true;
	}

	public List<List<Integer>> createAdjacencyList(int numCourses, int[][] prerequisites) {
		List<List<Integer>> adjacencyList = new ArrayList<>();
		for (int i = 0; i < numCourses; i++) {
			adjacencyList.add(new ArrayList<>());
		}

		for (int[] coursePreqArr : prerequisites) {
			List<Integer> coursePreqList = adjacencyList.get(coursePreqArr[0]);
			for (int i = 1; i < coursePreqArr.length; i++) {
				coursePreqList.add(coursePreqArr[i]);
			}
		}
		return adjacencyList;
	}
}