optimized_dijkstra | DOC graph search added

[Koubae]

Hi, I've find this repository really good, as I'm coding and learning new algorithm along, I think is a great Idea if I can also Optimized it and add some Documentation (which I Added as a README.MD, if another format for the DOCS is preferred please let me know)

As this is my first contribution in this repo I just added one example for Dijkstra and other algorithm, I have different one to share and there will be more if this first pull request is accepted.

Added

* I add a ShortestPathTree  in Dijkstra Class init as a NamedTuple, makes run the Algorithm slower but it outputs a really cool result for the Shortest-path tree.

* I added some documentation for Dijkstra Algorithm.

Optimized

* More Pythonic code.

* Readability and refactoring of the code

import timeit


test_1 = '''
from main import Dijkstra
g = Dijkstra(8+1)

g.graph = [[0, 4, 0, 0, 0, 0, 0, 8, 0],  # 0
           [4, 0, 8, 0, 0, 0, 0, 11, 0], # 1
           [0, 8, 0, 7, 0, 4, 0, 0, 2],  # 2
           [0, 0, 7, 0, 9, 14, 0, 0, 0],  # 3
           [0, 0, 0, 9, 0, 10, 0, 0, 0], # 4
           [0, 0, 4, 14, 10, 0, 2, 0, 0], # 5
           [0, 0, 0, 0, 0, 2, 0, 1, 6], # 6
           [8, 11, 0, 0, 0, 0, 1, 0, 7], # 7
           [0, 0, 2, 0, 0, 0, 6, 7, 0] # 8
           ]
'''

test_2 = '''
from main2 import Dijkstra_
g = Dijkstra_(8+1)

g.graph = [[0, 4, 0, 0, 0, 0, 0, 8, 0],  # 0
           [4, 0, 8, 0, 0, 0, 0, 11, 0], # 1
           [0, 8, 0, 7, 0, 4, 0, 0, 2],  # 2
           [0, 0, 7, 0, 9, 14, 0, 0, 0],  # 3
           [0, 0, 0, 9, 0, 10, 0, 0, 0], # 4
           [0, 0, 4, 14, 10, 0, 2, 0, 0], # 5
           [0, 0, 0, 0, 0, 2, 0, 1, 6], # 6
           [8, 11, 0, 0, 0, 0, 1, 0, 7], # 7
           [0, 0, 2, 0, 0, 0, 6, 7, 0] # 8
           ]
'''

print('Dijkstra', min(timeit.Timer(test_1).repeat(5, 100_000)))  # New Code
print('Dijkstra_',min(timeit.Timer(test_2).repeat(5, 100_000))) # Old Code
# New Code => Dijkstra 0.20088510000000004
# Old Code =>  Dijkstra_ 0.6164977

Added

* I run Faster! This is a result with a simple benchmark:

Signed-off-by: Koubae [email protected]