adding dijsktra algorithm #301

Kiran-Venkatesh · 2020-10-06T17:06:39Z

Fixes #153

Brief description of what is fixed or changed
I implemented the dijsktra algorithm . Added minDistance and dijkstra_algorithm function in pydatastructs.graphs.algorithms
Added test_dijkstra_algorithm and _test_dijkstra_algorithm in pydatastructs.graphs.tests.test_algorithms. I checked all export statements and init files to make sure it's working and also added system library for defining infinity value.

Other comments
I had a problem with relative directory in my python environment initially,but since it worked completely in this repo, I didn't change that. I'm making a PR for this first time.

prshnt19 · 2020-10-07T05:10:08Z

pydatastructs/graphs/adjacency_matrix.py

@@ -63,7 +63,7 @@ def add_edge(self, source, target, cost=None):
                GraphEdge(self.__getattribute__(source),
                          self.__getattribute__(target),
                          cost)
-
+            


The build is failing because of code quality.
Just remove the extra spaces here and use newline only.

Suggested change

prshnt19 · 2020-10-07T05:13:54Z

pydatastructs/graphs/algorithms.py

@@ -877,3 +879,73 @@ def _job(graph: Graph, u: str):
    if len(L) != num_vertices:
        raise ValueError("Graph is not acyclic.")
    return L
+
+def minDistance(graph: Graph,dist,visited,source):


Use spaces after ','.

Suggested change

def minDistance(graph: Graph,dist,visited,source):

def min_distance(graph: Graph, dist, visited, source):

prshnt19 · 2020-10-07T05:14:17Z

pydatastructs/graphs/algorithms.py

+    graph: Graph
+        The graph under consideration.
+    start: str
+        The name of the source the node.


Suggested change

The name of the source the node.

The name of the source node.

prshnt19 · 2020-10-07T05:28:52Z

pydatastructs/graphs/algorithms.py

@@ -877,3 +879,73 @@ def _job(graph: Graph, u: str):
    if len(L) != num_vertices:
        raise ValueError("Graph is not acyclic.")
    return L
+
+def minDistance(graph: Graph,dist,visited,source):
+    min = sys.maxsize


I think float('inf') is better alternative for sys.maxsize.

Suggested change

min = sys.maxsize

min = float('inf')

Kiran-Venkatesh · 2020-10-07T06:30:13Z

Thanks for the feedback

…

On Wed, Oct 7, 2020, 10:59 AM Prashant Rawat ***@***.***> wrote: ***@***.**** requested changes on this pull request. ------------------------------ In pydatastructs/graphs/adjacency_matrix.py <#301 (comment)> : > @@ -63,7 +63,7 @@ def add_edge(self, source, target, cost=None): GraphEdge(self.__getattribute__(source), self.__getattribute__(target), cost) - + The build is failing because of code quality. Just remove the extra spaces here and use newline only. ------------------------------ In pydatastructs/graphs/algorithms.py <#301 (comment)> : > @@ -877,3 +879,73 @@ def _job(graph: Graph, u: str): if len(L) != num_vertices: raise ValueError("Graph is not acyclic.") return L + +def minDistance(graph: Graph,dist,visited,source): Use spaces after ','. ------------------------------ In pydatastructs/graphs/algorithms.py <#301 (comment)> : > + if dist[v] < min and visited[v] is False: + min = dist[v] + min_index = v + return min_index + +def dijkstra_algorithm(graph: Graph,start: str): + """ + Finds shortest path distance in the given graph from a given source to all vertex. + + Parameters + ========== + + graph: Graph + The graph under consideration. + start: str + The name of the source the node. ⬇️ Suggested change - The name of the source the node. + The name of the source node. ------------------------------ In pydatastructs/graphs/algorithms.py <#301 (comment)> : > @@ -877,3 +879,73 @@ def _job(graph: Graph, u: str): if len(L) != num_vertices: raise ValueError("Graph is not acyclic.") return L + +def minDistance(graph: Graph,dist,visited,source): + min = sys.maxsize I think float('inf') is better alternative for sys.maxsize. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#301 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIUEACDZEQ3KNHRN7LT4AGTSJP4E5ANCNFSM4SGJTJDQ> .

czgdp1807 · 2020-10-07T08:41:12Z

pydatastructs/graphs/algorithms.py

+
+def minDistance(graph: Graph,dist,visited,source):
+    min = sys.maxsize
+    min_index=source


Suggested change

min_index=source

min_index = source

czgdp1807 · 2020-10-07T08:41:37Z

pydatastructs/graphs/algorithms.py

+            except:
+                pass
+
+    L={}


Suggested change

L={}

L = {}

czgdp1807 · 2020-10-07T08:42:54Z

pydatastructs/graphs/algorithms.py

+    V=len(graph.vertices)
+    visited={}
+    dist={}
+    for v in graph.vertices:
+        visited[v]=False
+        if v!=start:
+            dist[v] =sys.maxsize
+    dist[start] = 0
+
+    for cout in range(V):
+        u = minDistance(graph,dist,visited,start) 
+        visited[u] = True
+        for v in graph.vertices: 
+            try:
+                if graph.edge_weights[u+"_"+v].value> 0 and visited[v] is False and dist[v] > dist[u] + graph.edge_weights[u+"_"+v].value:
+                    dist[v] = dist[u] + graph.edge_weights[u+"_"+v].value
+            except:
+                pass


Suggested change

V=len(graph.vertices)

visited={}

dist={}

for v in graph.vertices:

visited[v]=False

if v!=start:

dist[v] =sys.maxsize

dist[start] = 0

for cout in range(V):

u = minDistance(graph,dist,visited,start)

visited[u] = True

for v in graph.vertices:

try:

if graph.edge_weights[u+"_"+v].value> 0 and visited[v] is False and dist[v] > dist[u] + graph.edge_weights[u+"_"+v].value:

dist[v] = dist[u] + graph.edge_weights[u+"_"+v].value

except:

pass

V = len(graph.vertices)

visited = {}

dist = {}

for v in graph.vertices:

visited[v] = False

if v != start:

dist[v] = float('inf')

dist[start] = 0

for cout in range(V):

u = min_distance(graph, dist, visited, start)

visited[u] = True

for v in graph.vertices:

edge_str = u + '_' + v

if (edge_str in graph.edge_weights and graph.edge_weights[edge_str].value > 0 and

visited[v] is False and dist[v] > dist[u] + graph.edge_weights[edge_str].value):

dist[v] = dist[u] + graph.edge_weights[edge_str].value

Why we need try-except block here?

this what meant to do?

this what meant to do?

This probably does what you wanted to do but without try-except. try-except shouldn't be used usually.

Kiran-Venkatesh · 2020-10-07T08:49:44Z

Try except is needed when edge_weights takes unknown vertex gives error

…

On Wed, Oct 7, 2020, 2:13 PM Gagandeep Singh ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In pydatastructs/graphs/algorithms.py <#301 (comment)> : > + V=len(graph.vertices) + visited={} + dist={} + for v in graph.vertices: + visited[v]=False + if v!=start: + dist[v] =sys.maxsize + dist[start] = 0 + + for cout in range(V): + u = minDistance(graph,dist,visited,start) + visited[u] = True + for v in graph.vertices: + try: + if graph.edge_weights[u+"_"+v].value> 0 and visited[v] is False and dist[v] > dist[u] + graph.edge_weights[u+"_"+v].value: + dist[v] = dist[u] + graph.edge_weights[u+"_"+v].value + except: + pass ⬇️ Suggested change - V=len(graph.vertices) - visited={} - dist={} - for v in graph.vertices: - visited[v]=False - if v!=start: - dist[v] =sys.maxsize - dist[start] = 0 - - for cout in range(V): - u = minDistance(graph,dist,visited,start) - visited[u] = True - for v in graph.vertices: - try: - if graph.edge_weights[u+"_"+v].value> 0 and visited[v] is False and dist[v] > dist[u] + graph.edge_weights[u+"_"+v].value: - dist[v] = dist[u] + graph.edge_weights[u+"_"+v].value - except: - pass + V = len(graph.vertices) + visited = {} + dist = {} + for v in graph.vertices: + visited[v] = False + if v != start: + dist[v] = float('inf') + dist[start] = 0 + + for cout in range(V): + u = min_distance(graph, dist, visited, start) + visited[u] = True + for v in graph.vertices: + try: + if graph.edge_weights[u+"_"+v].value > 0 and visited[v] is False and dist[v] > dist[u] + graph.edge_weights[u+"_"+v].value: + dist[v] = dist[u] + graph.edge_weights[u+"_"+v].value + except: + pass Why we need try-except block here? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#301 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIUEACHOQ4NJWUCRSZ33U3LSJQS2DANCNFSM4SGJTJDQ> .

czgdp1807 · 2020-10-07T08:57:06Z

pydatastructs/graphs/algorithms.py

+    dist[start] = 0
+
+    for cout in range(V):
+        u = minDistance(graph,dist,visited,start) 


Here we can use Fibonacci heap(see heaps in this repo). Right Now complexity will be O(V^2). After Fibonacci heap, it should be O(VlogV).

In pydatastructs/trees/heaps.py directory,there is no fibonacci heaps implementation,then whether have to remove min_distance function and include implementation of fibonacci heap in pydatastructs/graphs/algorithms.py.
or otherwise i will push this existing one?

You can use BinomialHeap in that case. What we need is a priority queue.

pydatastructs/pydatastructs/miscellaneous_data_structures/queue.py

Line 191 in 7138dc4

class PriorityQueue(object):

priority queue is it k to use in pydatastructs/pydatastructs/miscellaneous_data_structures/queue.py? to find the vertex which has minimum distance

or binomial heap is fine to use for finding vertex position which has minimum distance?

I would suggest to use 'binomial_heap' implementation of PriorityQueue(read its docs).

but inserting updated distances in binomial heap for all vertex takes O(V) time,then wats the use for O(logV) in this case?

included priorityqueue ,getting output in spyder but not here in CI/CD pipeline

Kiran-Venkatesh · 2020-10-07T08:58:54Z

Have to change initial part of Dijkstra algorithm?

…

On Wed, Oct 7, 2020, 2:27 PM Gagandeep Singh ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In pydatastructs/graphs/algorithms.py <#301 (comment)> : > + References + ========== + + .. [1] https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm#:~:text=Dijkstra's + """ + V=len(graph.vertices) + visited={} + dist={} + for v in graph.vertices: + visited[v]=False + if v!=start: + dist[v] =sys.maxsize + dist[start] = 0 + + for cout in range(V): + u = minDistance(graph,dist,visited,start) Here we can use Fibonacci heap(see heaps in this repo). Right Now complexity will be O(V^2). After Fibonacci heap, it should be O(VlogV). — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#301 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIUEACHP54ZC7WLJSTGWLFLSJQUPFANCNFSM4SGJTJDQ> .

pydatastructs/graphs/algorithms.py

pydatastructs/graphs/graph.py

pydatastructs/graphs/adjacency_matrix.py

pydatastructs/graphs/algorithms.py

pydatastructs/graphs/tests/test_algorithms.py

czgdp1807 · 2020-10-07T18:58:08Z

There are quite a lot of lines with trailing white spaces. Can you please remove those spaces? For spyder the following should help, (Preferences -> Editor -> Advanced settings:) "Automatically remove trailing spaces when saving files"

Kiran-Venkatesh · 2020-10-07T19:11:46Z

In Spyder,it works only when absolute path of libraries given, not relative path in pydatastructs/graphs/init_.py

…

On Thu, Oct 8, 2020, 12:28 AM Gagandeep Singh ***@***.***> wrote: There are quite a lot of lines with trailing white spaces. Can you please remove those spaces? For spyder the following should help, (Preferences -> Editor -> Advanced settings:) "Automatically remove trailing spaces when saving files" — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#301 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIUEACA257ZLPKWYLEIUGL3SJS25DANCNFSM4SGJTJDQ> .

Kiran-Venkatesh · 2020-10-08T13:55:53Z

removed trailing spaces and included binomial heap

pydatastructs/graphs/algorithms.py

codecov · 2020-10-10T19:23:09Z

Codecov Report

Merging #301 into master will increase coverage by 0.027%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##            master      #301       +/-   ##
=============================================
+ Coverage   98.827%   98.855%   +0.027%     
=============================================
  Files           25        25               
  Lines         2901      2970       +69     
=============================================
+ Hits          2867      2936       +69     
  Misses          34        34

Impacted Files	Coverage Δ
pydatastructs/graphs/algorithms.py	`99.450% <100.000%> (+0.042%)`	⬆️
pydatastructs/linear_data_structures/__init__.py	`100.000% <0.000%> (ø)`
pydatastructs/linear_data_structures/algorithms.py	`99.447% <0.000%> (+0.172%)`	⬆️

czgdp1807 · 2020-10-10T19:25:12Z

Thanks for your contributions.

Kiran-Venkatesh · 2020-10-10T19:28:11Z

Is that my code got merged? I was unable to push my updated code for last 4 days?

czgdp1807 · 2020-10-10T19:28:50Z

I made corrective changes by pushing to your branch(edits from maintainers).

Kiran-Venkatesh · 2020-10-10T19:29:09Z

Its gave some other contributer pushing my code

czgdp1807 · 2020-10-10T19:29:55Z

Please read, https://docs.github.com/en/free-pro-team@latest/github/collaborating-with-issues-and-pull-requests/allowing-changes-to-a-pull-request-branch-created-from-a-fork

czgdp1807 · 2020-10-10T19:38:44Z

Yes.

Kiran-Venkatesh · 2020-10-10T19:42:46Z

Okay thanks for guidance and support

…

On Sun, Oct 11, 2020, 1:08 AM Gagandeep Singh ***@***.***> wrote: Yes. — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub <#301 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIUEACHSFSFEMGBDWDKCEG3SKCZ47ANCNFSM4SGJTJDQ> .

Kiran-Venkatesh added 7 commits October 6, 2020 21:39

Adding dijsktra algorithm

88682a9

Adding dijsktra algorithm

dd14703

Added spacing in dijsktra algorithm

4ec02dd

Updated Adding dijsktra algorithm

8d23c69

Updated Adding dijsktra algorithm

9e7e793

Updated dijsktra algorithm

3d9d67f

Updated dijsktra algorithm

f999ee6

prshnt19 suggested changes Oct 7, 2020

View reviewed changes