Aya Bouchiha

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# Depth First Search (DFS) Algorithm

Hi, today, we're going to talk about Depth First Search (DFS)

## Definition of Depth First Search

• Depth First Search: is an algorithm for traversing or searching in tree or graph data structure using recursion and Stack data structure.

## Time & Space complexity of Depth First Search (DFS)

Space complexlity O(V)
Time complexity O(V+E)

## Depth First Search applications

• Counting connected components
• Solving Sudoku Puzzles
• Topological sorting
• Pathfinding
• Finding Strongly Connected Components of a graph

## Depth First Search implementation in Python

``````# code from https://www.educative.io/edpresso/how-to-implement-depth-first-search-in-python
graph = {
'A' : ['B','C'],
'B' : ['D', 'E'],
'C' : ['F'],
'D' : [],
'E' : ['F'],
'F' : []
}

visited = set() # Set to keep track of visited nodes.

def dfs(visited, graph, node):
if node not in visited:
print(node)
for neighbour in graph[node]:
dfs(visited, graph, neighbour)

dfs(visited, graph, 'A')
``````

#day_28