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I am creating a dijkstra algo. python code but this is the result when I try to run it.

  temp = min_heap[0][1]
IndexError: list index out of range


What to I need to change?

What I have tried:

def dijkstra(graph, source, destination):
    inf = sys.maxsize
    node_data = {'A': {'cost': inf, 'pred': []},
                 'B': {'cost': inf, 'pred': []},
                 'C': {'cost': inf, 'pred': []},
                 'D': {'cost': inf, 'pred': []},
                 'E': {'cost': inf, 'pred': []},
                 }
    node_data[source]['cost'] = 0
    visited = []
    temp = source
    for i in range(5):
        if temp not in visited:
            visited.append(temp)
            min_heap = []
            for j in graph[temp]:
                if j not in visited:
                    cost = node_data[temp]['cost'] + graph[temp][j]
                    if cost < node_data[j]['cost']:
                        node_data[j]['cost'] = cost
                        node_data[j]['pred'] = node_data[temp]['pred'] + [temp]
                    heappush(min_heap, (node_data[j]['cost'], j))
        heapify(min_heap)
        temp = min_heap[0][1]
    print("Shortest Distance: " + str(node_data[destination]['cost']))
    print("Shortest Path: " + str(node_data[destination]['pred'] + list(destination)))




if __name__ == "__main__":
    graph = {
        'A': {'B': 2, 'C': 3},
        'B': {'A': 2, 'C': 4, 'D': 7},
        'C': {'A': 3, 'B': 4, 'D': 2, 'E': 5},
        'D': {'B': 7, 'C': 2, 'E': 1},
        'E': {'C': 5, 'D': 1}
    }

    source = 'A'
    destination = 'F'
    dijkstra(graph, source, destination)
Posted
Updated 17-Jun-22 2:58am

1 solution

Quote:
I am creating a dijkstra algo. python code but this is the result when I try to run it.
temp = min_heap[0][1]
IndexError: list index out of range

Your code do not behave the way you expect, or you don't understand why !

There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

27.3. pdb — The Python Debugger — Python 3.6.1 documentation[^]
Debugging in Python | Python Conquers The Universe[^]
pdb – Interactive Debugger - Python Module of the Week[^]

The debugger is here to only show you what your code is doing and your task is to compare with what it should do.
 
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Comments
lil_mint 17-Jun-22 9:10am    
oh thanks for that.. I already found the mistake and it was "for i in range(5):" it should be 4. Thank you again.
Patrice T 17-Jun-22 9:25am    
Make it a solution and accept it.

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