# 1192. Critical Connections in a Network

<https://leetcode.com/problems/critical-connections-in-a-network>

## Description

There are `n` servers numbered from `0` to `n - 1` connected by undirected server-to-server `connections` forming a network where `connections[i] = [ai, bi]` represents a connection between servers `ai` and `bi`. Any server can reach other servers directly or indirectly through the network.

A *critical connection* is a connection that, if removed, will make some servers unable to reach some other server.

Return all critical connections in the network in any order.

**Example 1:**

![](https://assets.leetcode.com/uploads/2019/09/03/1537_ex1_2.png)

```
**Input:** n = 4, connections = [[0,1],[1,2],[2,0],[1,3]]
**Output:** [[1,3]]
**Explanation:** [[3,1]] is also accepted.
```

**Example 2:**

```
**Input:** n = 2, connections = [[0,1]]
**Output:** [[0,1]]
```

**Constraints:**

* `2 <= n <= 105`
* `n - 1 <= connections.length <= 105`
* `0 <= ai, bi <= n - 1`
* `ai != bi`
* There are no repeated connections.

## ac

```java
```


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