def topological(graph,start,path=[]):
    q = [start]
    while q:
        v = q.pop(0)
        if v not in path:
            path += [v]
            q = q + graph[v]
 
    return path
 
graph = {
    'a' : ['1','2','3','5'],#for 0 index
    '1' : ['4'],
    '2' : ['4'],
    '3' : ['4'],
    '4':  ['6','8'],
    '5' : ['6'],
    '6' : ['7'],
 
    '7' : ['9'],
    '8' : ['9'],
 
    '9' : []
}
sort = (topological(graph, 'a'))
print(sort)
 
 

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