> ## Documentation Index
> Fetch the complete documentation index at: https://leetcode-py.wisl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> leetcode-py is a Python LeetCode practice environment generator with one CLI: lcpy. It is not a service or platform.
> Each problem is a directory under leetcode/ with README.md, solution.py, test_solution.py, helpers.py, and playground.ipynb. lcpy gen creates them from JSON templates bundled with the package.
> Examples are backed by tests; copy them verbatim.

# Keys and Rooms Python Solution with Tests

> Tested Python solution for LeetCode 841 with 23 pytest cases. Generate a practice environment with lcpy.

LeetCode 841, [Medium](/catalog/medium). Topics: [Depth-First Search](/catalog/topics/depth-first-search), [Breadth-First Search](/catalog/topics/breadth-first-search), [Graph Theory](/catalog/topics/graph-theory). [View on LeetCode](https://leetcode.com/problems/keys-and-rooms/description/).

Generate this problem as a practice environment: tested reference solution, 23 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 841   # by problem number
lcpy gen -s keys_and_rooms   # by problem name
```

## Problem

There are `n` rooms labeled from `0` to `n - 1` and all the rooms are locked except for room `0`. Your goal is to visit all the rooms. However, you cannot enter a locked room without having its key.

When you visit a room, you may find a set of **distinct keys** in it. Each key has a number on it, denoting which room it unlocks, and you can take all of them with you to unlock the other rooms.

Given an array `rooms` where `rooms[i]` is the set of keys that you can obtain if you visited room `i`, return `true` if you can visit **all** the rooms, or `false` otherwise.

### Examples

```
Input: rooms = [[1],[2],[3],[]]
Output: true
Explanation:
We visit room 0 and pick up key 1.
We then visit room 1 and pick up key 2.
We then visit room 2 and pick up key 3.
We then visit room 3.
Since we were able to visit every room, we return true.
```

```
Input: rooms = [[1,3],[3,0,1],[2],[0]]
Output: false
Explanation: We can not enter room number 2 since the only key that unlocks it is in that room.
```

### Constraints

* n == rooms.length
* 2 \<= n \<= 1000
* 0 \<= rooms\[i].length \<= 1000
* 1 \<= sum(rooms\[i].length) \<= 3000
* 0 \<= rooms\[i]\[j] \< n
* All the values of rooms\[i] are unique.

## Solution

Reference implementation from [solution.py on GitHub](https://github.com/wislertt/leetcode-py/blob/main/leetcode/keys_and_rooms/solution.py), full suite in [test\_solution.py](https://github.com/wislertt/leetcode-py/blob/main/leetcode/keys_and_rooms/test_solution.py):

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
class Solution:
    # Time: O(n + k) where k is the total number of keys
    # Space: O(n)
    def can_visit_all_rooms(self, rooms: list[list[int]]) -> bool:
        visited = {0}
        stack = [0]
        while stack:
            room = stack.pop()
            for key in rooms[room]:
                if key not in visited:
                    visited.add(key)
                    stack.append(key)
        return len(visited) == len(rooms)
```

## Complexity

| Time | Space |
| - | - |
| O(n + k) where k is the total number of keys | O(n) |

## Tags


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