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python dijksta algorithm

Eno Umoh answered on July 28, 2022 Popularity 3/10 Helpfulness 3/10

answer python dijksta algorithm

python dijksta algorithm

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def dijkstra_algorithm(graph, start_node):
    unvisited_nodes = list(graph.get_nodes())
 
    # We'll use this dict to save the cost of visiting each node and update it as we move along the graph   
    shortest_path = {}
 
    # We'll use this dict to save the shortest known path to a node found so far
    previous_nodes = {}
 
    # We'll use max_value to initialize the "infinity" value of the unvisited nodes   
    max_value = sys.maxsize
    for node in unvisited_nodes:
        shortest_path[node] = max_value
    # However, we initialize the starting node's value with 0   
    shortest_path[start_node] = 0
    
    # The algorithm executes until we visit all nodes
    while unvisited_nodes:
        # The code block below finds the node with the lowest score
        current_min_node = None
        for node in unvisited_nodes: # Iterate over the nodes
            if current_min_node == None:
                current_min_node = node
            elif shortest_path[node] < shortest_path[current_min_node]:
                current_min_node = node
                
        # The code block below retrieves the current node's neighbors and updates their distances
        neighbors = graph.get_outgoing_edges(current_min_node)
        for neighbor in neighbors:
            tentative_value = shortest_path[current_min_node] + graph.value(current_min_node, neighbor)
            if tentative_value < shortest_path[neighbor]:
                shortest_path[neighbor] = tentative_value
                # We also update the best path to the current node
                previous_nodes[neighbor] = current_min_node
 
        # After visiting its neighbors, we mark the node as "visited"
        unvisited_nodes.remove(current_min_node)
    
    return previous_nodes, shortest_path

Popularity 3/10 Helpfulness 3/10 Language python

Source: www.udacity.com

Tags: algorithm python

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Contributed on Jul 28 2022

Eno Umoh

0 Answers Avg Quality 2/10

python dijksta algorithm

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