2022-05-14 12:28:36 +0000 UTC

class Solution {
   private final Map<Integer, List<Node>> connected = new HashMap<>();

    public int networkDelayTime(int[][] times, int n, int k) {
        for (int[] time : times) {
            connected.putIfAbsent(time[0], new ArrayList<>());
            connected.get(time[0]).add(new Node(time[2], time[1]));
        }
        connected.forEach((source, nodes) -> nodes.sort(Comparator.comparing(Node::travelTime)));
        int[] receivedTime = new int[n + 1]; Arrays.fill(receivedTime, 1, receivedTime.length, Integer.MAX_VALUE);
        dfs(receivedTime, 0, k);
        
        int max = Arrays.stream(receivedTime).max().orElseThrow(RuntimeException::new);
        return max == Integer.MAX_VALUE ? -1 : max;
    }

    private void dfs(int[] receivedTime, int currentTime, int currentNode) {
        if (receivedTime[currentNode] <= currentTime) return;
        receivedTime[currentNode] = currentTime;
        if (connected.containsKey(currentNode))
            connected.get(currentNode).forEach(node -> dfs(receivedTime, currentTime + node.travelTime(), node.destination()));
    }

    public record Node(int travelTime, int destination) {}
}