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# Python program for Dijkstra's single |
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# source shortest path algorithm. The program is |
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# for adjacency matrix representation of the graph |
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# Library for INT_MAX |
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import sys |
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class Graph(): |
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def __init__(self, vertices): |
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self.V = vertices |
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self.graph = [[0 for column in range(vertices)] |
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for row in range(vertices)] |
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def printSolution(self, dist): |
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print "Vertex tDistance from Source" |
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for node in range(self.V): |
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print node, "t", dist[node] |
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# A utility function to find the vertex with |
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# minimum distance value, from the set of vertices |
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# not yet included in shortest path tree |
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def minDistance(self, dist, sptSet): |
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# Initilaize minimum distance for next node |
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min = sys.maxint |
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# Search not nearest vertex not in the |
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# shortest path tree |
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for v in range(self.V): |
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if dist[v] < min and sptSet[v] == False: |
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min = dist[v] |
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min_index = v |
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return min_index |
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# Funtion that implements Dijkstra's single source |
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# shortest path algorithm for a graph represented |
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# using adjacency matrix representation |
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def dijkstra(self, src): |
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dist = [sys.maxint] * self.V |
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dist[src] = 0 |
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sptSet = [False] * self.V |
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for cout in range(self.V): |
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# Pick the minimum distance vertex from |
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# the set of vertices not yet processed. |
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# u is always equal to src in first iteration |
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u = self.minDistance(dist, sptSet) |
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# Put the minimum distance vertex in the |
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# shotest path tree |
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sptSet[u] = True |
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# Update dist value of the adjacent vertices |
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# of the picked vertex only if the current |
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# distance is greater than new distance and |
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# the vertex in not in the shotest path tree |
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for v in range(self.V): |
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if self.graph[u][v] > 0 and sptSet[v] == False and \ |
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dist[v] > dist[u] + self.graph[u][v]: |
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dist[v] = dist[u] + self.graph[u][v] |
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self.printSolution(dist) |
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# Driver program |
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g = Graph(9) |
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g.graph = [[0, 4, 0, 0, 0, 0, 0, 8, 0], |
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[4, 0, 8, 0, 0, 0, 0, 11, 0], |
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[0, 8, 0, 7, 0, 4, 0, 0, 2], |
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[0, 0, 7, 0, 9, 14, 0, 0, 0], |
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[0, 0, 0, 9, 0, 10, 0, 0, 0], |
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[0, 0, 4, 14, 10, 0, 2, 0, 0], |
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[0, 0, 0, 0, 0, 2, 0, 1, 6], |
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[8, 11, 0, 0, 0, 0, 1, 0, 7], |
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[0, 0, 2, 0, 0, 0, 6, 7, 0] |
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]; |
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g.dijkstra(0); |
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