#### Connected Components

```"""
https://en.wikipedia.org/wiki/Component_(graph_theory)

Finding connected components in graph

"""

test_graph_1 = {0: [1, 2], 1: [0, 3], 2: , 3: , 4: [5, 6], 5: [4, 6], 6: [4, 5]}

test_graph_2 = {0: [1, 2, 3], 1: [0, 3], 2: , 3: [0, 1], 4: [], 5: []}

def dfs(graph: dict, vert: int, visited: list) -> list:
"""
Use depth first search to find all vertices
being in the same component as initial vertex
>>> dfs(test_graph_1, 0, 5 * [False])
[0, 1, 3, 2]
>>> dfs(test_graph_2, 0, 6 * [False])
[0, 1, 3, 2]
"""

visited[vert] = True
connected_verts = []

for neighbour in graph[vert]:
if not visited[neighbour]:
connected_verts += dfs(graph, neighbour, visited)

return [vert, *connected_verts]

def connected_components(graph: dict) -> list:
"""
This function takes graph as a parameter
and then returns the list of connected components
>>> connected_components(test_graph_1)
[[0, 1, 3, 2], [4, 5, 6]]
>>> connected_components(test_graph_2)
[[0, 1, 3, 2], , ]
"""

graph_size = len(graph)
visited = graph_size * [False]
components_list = []

for i in range(graph_size):
if not visited[i]:
i_connected = dfs(graph, i, visited)
components_list.append(i_connected)

return components_list

if __name__ == "__main__":
import doctest

doctest.testmod()
```  