Network Delay Time

Medium

You are given directed weighted edges times where times[i] = [u, v, w], n nodes labeled 1..n, and a source k. Return the time for all nodes to receive a signal from k, or -1 if some node is unreachable.

Example 1

Input:  times = [[2,1,1],[2,3,1],[3,4,1]], n = 4, k = 2
Output: 2

Example 2

Input:  times = [[1,2,1]], n = 2, k = 2
Output: -1

Constraints

• 1 <= n <= 100
• 1 <= times.length <= 6000
• The graph is directed with positive weights.