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rosalind solutions/Connected Components/connectedcomponents.py

+#!/usr/bin/env/python3
+
+"""
+Name = Siu Pui Chung Jacky
+Student number = 1047527
+Script for Connected Components
+input: A simple directed graph with n≤103 vertices in the edge list format.
+output: The number of connected components in the graph.
+"""
+
+from sys import argv
+
+def producegraph(edgelist):
+    """
+    Description: store edgelist as dictionary
+    Input: edgelist, bi directional simple graph in edge list format
+    Output: numvertices, int of number of vertices in the graph
+            graphdict, dictioanry of uni-directed graph
+    """
+    graph = {}
+    #initialise default list
+    numvertices, edge = map(int, f.readline().strip().split(" "))
+    graph = {i+1:[] for i in range(numvertices)}
+    for line in edgelist:
+        line = line.strip()
+        key, value = int(line.split()[0]), int(line.split()[1])
+        #bi directional hence it can be value and key at the same time
+        graph[key].append(value)
+        graph[value].append(key)
+    return numvertices, graph
+    
+def dfs(vertex, connected_component, graphdict):
+    """
+    Description: recursive algorithm that connect connectable components
+    Input: vertex, current vertex being inspected
+            connected_component, empty list of connected componenets associated
+            with current vertex
+            graphdict, dictionaryof uni-directed graph
+    Output: connected_component, list of connected componenets associated
+            with current vertex
+    """
+    visited[vertex] = True
+    connected_component.append(vertex)
+    #recursive part which applies dfs function to neighbours of current vertex
+    for neighbour in graphdict[vertex]:
+        if visited[neighbour] == False:
+            connected_component = dfs(neighbour, connected_component, graphdict)
+    return connected_component
+
+if __name__ == "__main__":
+    with open(argv[1]) as f:
+        numvertices, graphdict = producegraph(f)
+        f.close()
+    print(graphdict)
+    #set all vertex in visited as False
+    visited = [False for i in range(numvertices+1)]
+    connected_component_list = []
+    for vertex in range(1, (numvertices + 1)):
+        #break up non-connected components by initilizing connected_component
+        if visited[vertex] == False:
+            connected_component = []
+            connected_component_list.append(dfs(vertex, connected_component, graphdict))
+    print(connected_component_list)
+    print(len(connected_component_list))
+    
+