public class Solution
extends Object
743 - Network Delay Time\.
Medium
You are given a network of `n` nodes, labeled from `1` to `n`. You are also given `times`, a list of travel times as directed edges times[i] = (ui, vi, wi), where ui is the source node, vi is the target node, and wi is the time it takes for a signal to travel from source to target.
We will send a signal from a given node `k`. Return the time it takes for all the `n` nodes to receive the signal. If it is impossible for all the `n` nodes to receive the signal, return `-1`.
**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 = 1
**Output:** 1
**Example 3:**
**Input:** times = \[\[1,2,1]], n = 2, k = 2
**Output:** -1
**Constraints:**
* `1 <= k <= n <= 100`
* `1 <= times.length <= 6000`
* `times[i].length == 3`
* 1 <= ui, vi <= n
* ui != vi
* 0 <= wi <= 100
* All the pairs (ui, vi) are **unique**. (i.e., no multiple edges.)