Create graphs/dijkstra_alternate.py (#7405)

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Co-authored-by: Christian Clauss <[email protected]>

* Update graphs/dijkstra.py

Co-authored-by: Christian Clauss <[email protected]>

* Update graphs/dijkstra.py

Co-authored-by: Christian Clauss <[email protected]>

* Update dijkstra.py

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* int(1e7)

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <[email protected]>