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Commit cb5467c

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Depth first search in Python
1 parent 6094903 commit cb5467c

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7 files changed

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# Copyright (C) Deepali Srivastava - All Rights Reserved
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# This code is part of DSA course available on CourseGalaxy.com
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INITIAL = 0
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VISITED = 1
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FINISHED = 2
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class Vertex:
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def __init__(self, name):
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self.name = name
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class UndirectedGraph:
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hasCycle = False
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def __init__(self,size=20):
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self._adj = [ [0 for column in range(size)] for row in range(size) ]
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self._n = 0
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self._vertexList = []
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def display(self):
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for i in range(self._n):
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for j in range(self._n):
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print( self._adj[i][j], end =' ')
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print()
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def numVertices(self):
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return self._n
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def numEdges(self):
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e = 0
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for i in range(self._n):
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for j in range(i):
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if self._adj[i][j]!=0:
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e+=1
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return e
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def vertices(self):
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return [vertex.name for vertex in self._vertexList]
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def edges(self):
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edges = []
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for i in range(self._n):
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for j in range(i):
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if self._adj[i][j] != 0:
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edges.append( (self._vertexList[i].name, self._vertexList[j].name) )
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return edges
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def _getIndex(self,s):
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index = 0
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for name in (vertex.name for vertex in self._vertexList):
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if s == name:
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return index
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index += 1
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return None
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def insertVertex(self,name):
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if name in (vertex.name for vertex in self._vertexList): ########
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print("Vertex with this name already present in the graph")
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return
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self._vertexList.append( Vertex(name) )
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self._n += 1
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def removeVertex(self,name):
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u = self._getIndex(name)
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if u is None:
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print("Vertex not present in the graph")
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return
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self._adj.pop(u)
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for i in range(self._n):
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self._adj[i].pop(u)
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for i,vertex in enumerate(self._vertexList):
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if name == vertex.name:
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self._vertexList.pop(i)
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self._n -= 1
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def insertEdge(self, s1, s2):
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u = self._getIndex(s1)
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v = self._getIndex(s2)
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if u is None:
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print("Start vertex not present in the graph, first insert the start vertex")
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elif v is None:
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print("End vertex not present in the graph, first insert the end vertex")
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elif u == v:
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print("Not a valid edge")
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elif self._adj[u][v] != 0 :
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print("Edge already present in the graph")
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else:
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self._adj[u][v] = 1
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self._adj[v][u] = 1
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def removeEdge(self, s1,s2):
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u = self._getIndex(s1)
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v = self._getIndex(s2)
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if u is None:
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print("Start vertex not present in the graph")
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elif v is None:
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print("End vertex not present in the graph")
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elif self._adj[u][v] == 0:
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print("Edge not present in the graph")
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else:
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self._adj[u][v] = 0
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self._adj[v][u] = 0
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def isAdjacent(self, s1, s2):
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u = self._getIndex(s1)
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v = self._getIndex(s2)
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if u is None:
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print("Start vertex not present in the graph")
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return False
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elif v is None:
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print("End vertex not present in the graph")
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return False
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return False if self._adj[u][v] == 0 else True
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def degree(self,s):
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u = self._getIndex(s)
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if u is None:
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print("Vertex not present in the graph")
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return
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deg = 0
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for v in range(self._n):
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if self._adj[u][v] != 0 :
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deg += 1
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return deg
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def dfsTraversal(self):
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s = input("Enter starting vertex for Depth First Search : ")
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u = self._getIndex(s)
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if u is None:
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print("Vertex not present in the graph")
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return
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for v in range(self._n):
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self._vertexList[v].state = INITIAL
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self._vertexList[v].predecessor = None
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self._dfs( u )
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print()
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def _dfs(self,v):
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self._vertexList[v].state = VISITED
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for i in range(self._n):
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if self._adj[v][i]!=0 and self._vertexList[v].predecessor != i:
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if self._vertexList[i].state == INITIAL:
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self._vertexList[i].predecessor = v
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print("Tree edge - " , self._vertexList[v].name , "," , self._vertexList[i].name)
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self._dfs(i)
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elif self._vertexList[i].state == VISITED:
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print("Back edge - " , self._vertexList[v].name ,"," , self._vertexList[i].name)
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self._vertexList[v].state = FINISHED
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def dfsTraversalAll(self):
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s = input("Enter starting vertex for Depth First Search : ")
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u = self._getIndex(s)
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if u is None:
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print("Vertex not present in the graph")
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return
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for v in range(self._n):
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self._vertexList[v].state = INITIAL
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self._vertexList[v].predecessor = None
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self._dfs(u)
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for v in range(self._n):
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if self._vertexList[v].state == INITIAL:
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self._dfs(v)
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print()
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def isCyclic(self):
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for v in range(self._n):
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self._vertexList[v].state = INITIAL
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UndirectedGraph.hasCycle = False
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for v in range(self._n):
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if self._vertexList[v].state == INITIAL:
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self._dfsC(v)
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return UndirectedGraph.hasCycle
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def _dfsC(self,v):
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self._vertexList[v].state = VISITED
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for i in range(self._n):
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if self._adj[v][i]!=0 and self._vertexList[v].predecessor != i:
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if self._vertexList[i].state == INITIAL:
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self._vertexList[i].predecessor = v
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self._dfsC(i)
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elif self._vertexList[i].state == VISITED:
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UndirectedGraph.hasCycle = True
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self._vertexList[v].state = FINISHED
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if __name__ == '__main__':
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g = UndirectedGraph()
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g.insertVertex("Zero")
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g.insertVertex("One")
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g.insertVertex("Two")
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g.insertVertex("Three")
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g.insertVertex("Four")
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g.insertVertex("Five")
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g.insertVertex("Six")
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g.insertVertex("Seven")
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g.insertVertex("Eight")
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g.insertVertex("Nine")
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g.insertVertex("Ten")
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g.insertVertex("Eleven")
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g.insertVertex("Twelve")
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g.insertVertex("Thirteen")
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g.insertVertex("Fourteen")
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g.insertEdge("Zero","One")
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g.insertEdge("Zero","Three")
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g.insertEdge("One","Two")
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g.insertEdge("One","Three")
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g.insertEdge("One","Four")
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g.insertEdge("Three","Four")
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g.insertEdge("Five","Six")
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g.insertEdge("Five","Seven")
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g.insertEdge("Five","Eight")
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g.insertEdge("Seven","Eight")
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g.insertEdge("Nine","Ten")
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g.insertEdge("Nine","Eleven")
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g.insertEdge("Nine","Twelve")
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g.insertEdge("Nine","Thirteen")
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g.insertEdge("Ten","Twelve")
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g.insertEdge("Eleven","Thirteen")
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g.insertEdge("Eleven","Fourteen")
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g.dfsTraversalAll()
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if g.isCyclic():
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print("Graph is Cyclic")
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else:
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print("Graph is Acylic")
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