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ivanmmarkovicivanmmarkovic
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organizing project
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‎Ch07. Graphs and Graph Algorithms/dijkstra/dijkstra dense graphs/graph.py‎

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from vertex import Vertex
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class Graph:
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def __init__(self, size: int = 10):
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self.vertices: list = []
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self.adjacencyMatrix = [[float("inf") for x in range(size)] for y in range(size)]
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self.adjacencyList: dict = {}
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self.prev: dict = {}
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self.visited: dict = {}
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def addVertex(self, label: str, weight:int = float("inf")):
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vertex: Vertex = Vertex(label, weight)
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vertex.index = len(self.vertices)
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self.vertices.append(vertex)
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self.prev[label] = None
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self.adjacencyList[label] = []
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self.visited[label] = False
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def addEdge(self, label1: str, label2: str, weight: int):
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index1: int = self.findIndexByLabel(label1)
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index2: int = self.findIndexByLabel(label2)
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self.adjacencyMatrix[index1][index2] = weight
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def dijkstra(self, label: str):
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index: int = self.findIndexByLabel(label)
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current: Vertex = self.vertices[index]
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current.weight = 0
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while current is not None:
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for i in range(len(self.adjacencyMatrix[current.index])):
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if self.adjacencyMatrix[current.index][i] != float("inf"):
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if current.weight + self.adjacencyMatrix[current.index][i] < self.vertices[i].weight:
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self.vertices[i].weight = current.weight + self.adjacencyMatrix[current.index][i]
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self.prev[self.vertices[i].label] = current.label
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self.visited[current.label] = True
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current: Vertex = self.findCheapestVertex()
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def findCheapestVertex(self)->Vertex:
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current: Vertex = None
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for vertex in self.vertices:
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if self.visited[vertex.label] == False:
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if current is None:
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current = vertex
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elif current.weight > vertex.weight:
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current = vertex
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return current
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def showPath(self, label: str)->str:
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if self.prev[label] is None:
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return label
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else:
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return self.showPath(self.prev[label]) + " -> " + label
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def findIndexByLabel(self, label: str)->int:
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found: bool = False
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count: int = 0
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while count < len(self.vertices) and not found:
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if self.vertices[count].label == label:
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found = True
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else:
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count += 1
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if found:
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return count
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else:
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return None
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‎Ch07. Graphs and Graph Algorithms/dijkstra/dijkstra dense graphs/main.py‎

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from graph import Graph
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graph = Graph()
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graph.addVertex("START")
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graph.addVertex("A")
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graph.addVertex("C")
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graph.addVertex("B")
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graph.addVertex("D")
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graph.addVertex("END")
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graph.addEdge("START", "A", 0)
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graph.addEdge("START", "C", 2)
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graph.addEdge("A", "B", 18)
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graph.addEdge("A", "D", 15)
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graph.addEdge("C", "B", 3)
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graph.addEdge("C", "D", 10)
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graph.addEdge("B", "END", 150)
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graph.addEdge("D", "END", 15)
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graph.dijkstra("START")
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print(graph.showPath("END"))

‎Ch07. Graphs and Graph Algorithms/dijkstra/dijkstra dense graphs/vertex.py‎

Lines changed: 7 additions & 0 deletions
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class Vertex:
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def __init__(self, label: str = None, weight: int = None, index: int = None, key: int = None):
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self.label = label
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self.weight = weight
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self.index = index
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self.key = key

‎Ch07. Graphs and Graph Algorithms/dijkstra/dijkstra priority queue/graph.py‎

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from vertex import Vertex
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from priorityqueue import PriorityQueue
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class Graph:
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def __init__(self):
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self.vertices: list = []
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self.adjacencyList: dict = {}
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self.prev: dict = {}
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def addVertex(self, label: str, weight:int = float("inf")):
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vertex: Vertex = Vertex(label, weight)
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vertex.index = len(self.vertices)
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self.vertices.append(vertex)
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self.prev[label] = None
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self.adjacencyList[label] = []
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def addEdge(self, label1: str, label2: str, weight: int):
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vertex: Vertex = Vertex(label2, weight)
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index: int = self.findIndexByLabel(label2)
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vertex.index = index
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self.adjacencyList[label1].append(vertex)
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def dijkstra(self, label: str):
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index: int = self.findIndexByLabel(label)
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self.vertices[index].weight = 0
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pq = PriorityQueue()
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pq.buildHeap(self.vertices)
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current: Vertex
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while not pq.isEmpty():
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current = pq.deleteMin()
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for neighbour in self.adjacencyList[current.label]:
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if current.weight + neighbour.weight < self.vertices[neighbour.index].weight:
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self.prev[self.vertices[neighbour.index].label] = current.label
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self.vertices[neighbour.index].weight = current.weight + neighbour.weight
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pq.decreaseKey(self.vertices[neighbour.index].key)
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def showPath(self, label: str)->str:
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if self.prev[label] is None:
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return label
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else:
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return self.showPath(self.prev[label]) + " -> " + label
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def findIndexByLabel(self, label: str)->int:
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found: bool = False
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count: int = 0
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while count < len(self.vertices) and not found:
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if self.vertices[count].label == label:
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found = True
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else:
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count += 1
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if found:
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return count
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else:
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return None
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‎Ch07. Graphs and Graph Algorithms/dijkstra/dijkstra priority queue/main.py‎

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from graph import Graph
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graph = Graph()
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graph.addVertex("START")
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graph.addVertex("A")
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graph.addVertex("C")
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graph.addVertex("B")
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graph.addVertex("D")
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graph.addVertex("END")
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graph.addEdge("START", "A", 0)
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graph.addEdge("START", "C", 2)
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graph.addEdge("A", "B", 18)
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graph.addEdge("A", "D", 15)
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graph.addEdge("C", "B", 3)
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graph.addEdge("C", "D", 10)
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graph.addEdge("B", "END", 150)
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graph.addEdge("D", "END", 15)
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graph.dijkstra("START")
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print(graph.showPath("END"))

‎Ch07. Graphs and Graph Algorithms/dijkstra/dijkstra priority queue/priorityqueue.py‎

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from vertex import Vertex
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class PriorityQueue:
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def __init__(self, size: int = 0):
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self.heap: list = [None]
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self.size = size
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def isEmpty(self)->bool:
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return self.size == 0
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def insert(self, vertex: Vertex):
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self.size += 1
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vertex.key = self.size
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self.heap.append(vertex)
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self.percUp(self.size)
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def percUp(self, index: int):
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while index // 2 > 0:
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if self.heap[index].weight < self.heap[index//2].weight:
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self.heap[index], self.heap[index//2] = self.heap[index//2], self.heap[index]
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self.heap[index].key = index
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self.heap[index//2].key = index // 2
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index = index // 2
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def decreaseKey(self, index):
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self.percUp(index)
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def deleteMin(self)->Vertex:
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if self.isEmpty():
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return None
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else:
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tmp: Vertex = self.heap[1]
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self.heap[1] = self.heap[self.size]
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self.heap[1].key = 1
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self.heap.pop()
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self.size -= 1
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self.percDown(1)
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return tmp
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def percDown(self, index: int):
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while index * 2 <= self.size:
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minIndex: int = self.getMinIndex(index)
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if self.heap[index].weight > self.heap[minIndex].weight:
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self.heap[index], self.heap[minIndex] = self.heap[minIndex], self.heap[index]
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self.heap[index].key = index
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self.heap[minIndex].key = minIndex
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index = minIndex
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def getMinIndex(self, index: int):
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if index * 2 + 1 > self.size:
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return index * 2
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else:
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if self.heap[index * 2].weight <= self.heap[index * 2 + 1].weight:
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return index * 2
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else:
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return index * 2 + 1
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def buildHeap(self, vertices: list):
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for vertex in vertices:
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self.insert(vertex)

‎Ch07. Graphs and Graph Algorithms/dijkstra/dijkstra priority queue/vertex.py‎

Lines changed: 7 additions & 0 deletions
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class Vertex:
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def __init__(self, label: str = None, weight: int = None, index: int = None, key: int = None):
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self.label = label
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self.weight = weight
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self.index = index
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self.key = key

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