mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-12-18 09:10:16 +00:00
9200a2e543
* from __future__ import annotations
* fixup! from __future__ import annotations
* fixup! from __future__ import annotations
* fixup! Format Python code with psf/black push
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
50 lines
1.4 KiB
Python
50 lines
1.4 KiB
Python
"""Non recursive implementation of a DFS algorithm."""
|
|
|
|
from __future__ import annotations
|
|
|
|
|
|
def depth_first_search(graph: dict, start: str) -> set[int]:
|
|
"""Depth First Search on Graph
|
|
:param graph: directed graph in dictionary format
|
|
:param vertex: starting vertex as a string
|
|
:returns: the trace of the search
|
|
>>> G = { "A": ["B", "C", "D"], "B": ["A", "D", "E"],
|
|
... "C": ["A", "F"], "D": ["B", "D"], "E": ["B", "F"],
|
|
... "F": ["C", "E", "G"], "G": ["F"] }
|
|
>>> start = "A"
|
|
>>> output_G = list({'A', 'B', 'C', 'D', 'E', 'F', 'G'})
|
|
>>> all(x in output_G for x in list(depth_first_search(G, "A")))
|
|
True
|
|
>>> all(x in output_G for x in list(depth_first_search(G, "G")))
|
|
True
|
|
"""
|
|
explored, stack = set(start), [start]
|
|
|
|
while stack:
|
|
v = stack.pop()
|
|
explored.add(v)
|
|
# Differences from BFS:
|
|
# 1) pop last element instead of first one
|
|
# 2) add adjacent elements to stack without exploring them
|
|
for adj in reversed(graph[v]):
|
|
if adj not in explored:
|
|
stack.append(adj)
|
|
return explored
|
|
|
|
|
|
G = {
|
|
"A": ["B", "C", "D"],
|
|
"B": ["A", "D", "E"],
|
|
"C": ["A", "F"],
|
|
"D": ["B", "D"],
|
|
"E": ["B", "F"],
|
|
"F": ["C", "E", "G"],
|
|
"G": ["F"],
|
|
}
|
|
|
|
if __name__ == "__main__":
|
|
import doctest
|
|
|
|
doctest.testmod()
|
|
print(depth_first_search(G, "A"))
|