define a function to create a eulerian cycle in python

main.py
def eulerian_cycle(graph):
    """
    This function takes a graph represented as a dictionary
    and returns an Eulerian cycle if one exists.
    """
    cycle = []  # initialize the cycle to be empty
    stack = []  # initialize the stack to be empty
    
    # choose any vertex as the starting point
    start_vertex = list(graph.keys())[0]  
    
    # add the first vertex to the stack
    stack.append(start_vertex)  
    
    while stack:
        current_vertex = stack[-1]
        
        # if there are no more edges from current vertex
        # remove it from the stack and add it to the cycle
        if not graph[current_vertex]:
            cycle.append(stack.pop())
        
        # otherwise, visit the next vertex on the path
        else:
            next_vertex = graph[current_vertex].pop()
            stack.append(next_vertex)
    
    # finally, reverse the cycle to get a valid Eulerian cycle
    cycle.reverse()  
    
    # check that every edge is visited
    for vertex in graph:
        if graph[vertex]:
            return None
    
    return cycle  # return Eulerian cycle
1110 chars
37 lines