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Author: ivanmmarkovic

Ch07. Graphs and Graph Algorithms/DepthFirstSearch/Graph.py

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+from Vertex import Vertex
+from Stack import Stack
+
+class Graph:
+    def __init__(self, maxNumberOfVertices = 0):
+        self.maxNumberOfVertices = maxNumberOfVertices
+        self.vertices = [None] * maxNumberOfVertices
+        self.currentNumberOfVertices = 0
+        self.adjacencyMatrix = [[0 for x in range(maxNumberOfVertices)] for y in range(maxNumberOfVertices)]
+
+    def addVertex(self, label):
+        vertex = Vertex(label, self.currentNumberOfVertices)
+        self.vertices[self.currentNumberOfVertices] = vertex
+        self.adjacencyMatrix[self.currentNumberOfVertices][self.currentNumberOfVertices] = False
+        self.currentNumberOfVertices += 1
+
+    def addEdge(self, start, end):
+        self.adjacencyMatrix[start][end] = True
+        self.adjacencyMatrix[end][start] = True
+
+    def findNeigbour(self, vertex):
+        for j in range(self.currentNumberOfVertices):
+            if self.adjacencyMatrix[vertex.index][j] == True and self.vertices[j].visited == False:
+                return j
+        return -1
+
+    def breadthFirstSearch(self):
+        stack = Stack()
+        vertex = self.vertices[0]
+        vertex.visited = True
+        stack.push(vertex)
+        while not stack.isEmpty():
+            currentVertex = stack.peek()
+            print("Visiting : " + currentVertex.label)
+            index = self.findNeigbour(currentVertex)
+            if index != -1:
+                self.vertices[index].visited = True
+                stack.push(self.vertices[index])
+            else:
+                stack.pop()
+
+graph = Graph(10)
+
+graph.addVertex("A")
+graph.addVertex("B")
+graph.addVertex("C")
+graph.addVertex("D")
+graph.addVertex("E")
+
+graph.addEdge(0, 1) # AB
+graph.addEdge(0, 2) # AC
+graph.addEdge(0, 3) # AD
+graph.addEdge(1, 2) # BC
+graph.addEdge(2, 1) # CB
+graph.addEdge(2, 4) # CE
+graph.addEdge(3, 4) # DE
+
+graph.breadthFirstSearch()

Ch07. Graphs and Graph Algorithms/DepthFirstSearch/Stack.py

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+class Stack:
+    def __init__(self):
+        self.items = []
+
+    def isEmpty(self):
+        return self.items == []
+
+    def push(self, item):
+        self.items.append(item)
+
+    def pop(self):
+        return self.items.pop()
+
+    def peek(self):
+        return self.items[len(self.items) - 1]
+
+    def size(self):
+        return len(self.items)

Ch07. Graphs and Graph Algorithms/DepthFirstSearch/Vertex.py

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+class Vertex:
+    def __init__(self, label = None, index = None):
+        self.label = label
+        self.index = index
+        self.visited = False
+        self.inserted = False