DFS implemented (using the BFS API)

[HarsheetKakar]

References to other Issues or PRs or Relevant literature

Fixes #111

Brief description of what is fixed or changed

Other comments

[codecov]

Codecov Report

Merging #253 into master will increase coverage by 0.016%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##            master      #253       +/-   ##
=============================================
+ Coverage   98.546%   98.563%   +0.016%     
=============================================
  Files           24        24               
  Lines         2202      2228       +26     
=============================================
+ Hits          2170      2196       +26     
  Misses          32        32               

Impacted Files	Coverage Δ
pydatastructs/graphs/__init__.py	100.000% <ø> (ø)
pydatastructs/graphs/algorithms.py	100.000% <100.000%> (ø)

[HarsheetKakar]

sir is there any benefit of using .get method instead of simply checking the key

[czgdp1807]

In fact, in is better at least for numbers.

>>> d = {k: v for k, v in zip(range(10**7), range(10**7))}
>>> import timeit
>>> def f():
...     return 10**6 in d
... 
>>> def g():
...     return d.get(10**6, None)
... 
>>> timeit.timeit(f)
0.09641253299923846
>>> timeit.timeit(g)
0.14119643199956045

[HarsheetKakar]

In fact, in is better at least for numbers.

>>> d = {k: v for k, v in zip(range(10**7), range(10**7))}
>>> import timeit
>>> def f():
...     return 10**6 in d
... 
>>> def g():
...     return d.get(10**6, None)
... 
>>> timeit.timeit(f)
0.09641253299923846
>>> timeit.timeit(g)
0.14119643199956045

thats a good chunk of time saved, never thought it would have that.

[czgdp1807]

Merging.