dag.py

import sys 
def main():
    #Read Arguments
    arch = sys.argv[1]
    #print("Nombre archivo",arch)
    #Read file
    file = open(arch, "r").read()

    #replace \n  to whitespace
    file = file.replace('\n',' ')

    #Split file
    arr = file.split(' ')
    #Remove empty lines
    arr = list(filter(None, arr))
    #print(arr)
    
    #Create the hash map
    dict_ = create_hash(arr)

    #print(dict_.keys())
    #Check every key
    cycle = False
    for k in dict_.keys():
        #print("Voy a buscar ciclo para",k)
        cycle = recurs(dict_, k,k,[])
        if cycle:
            break

    if cycle:
        print("Si")
    else:
        print("No")


"""
Create a dictionary of the accesible nodes for each node
"""
def create_hash(arr):
    dict_ = {}
    for pair in arr:
        key =  pair.split(',')[0]
        value = pair.split(',')[1]
        if key in dict_:
            dict_[key].append(value)
        else:
            dict_[key] = list(value)
    return dict_            
   
"""
Recursion where we found a cycle
"""
def recurs(dict_, goal, act_k, passed):

    #print("Estoy en %s"%(act_k))
    #print("%s conecta con %s? %s"%(act_k, goal, goal in dict_[act_k]))
    if goal in dict_[act_k]:
        return True
    else:
        #Iterate over the posible paths     
        for i in range(len(dict_[act_k])):
            #print("%s-%s"%(act_k, i))
            temp_k = dict_[act_k][i]
            #print("He pasado por %s, no esta %s ahi?: %s"%(passed, temp_k, str(temp_k) not in passed))
            if (temp_k in dict_.keys()) and(str(temp_k) not in passed):
                passed.append(temp_k)
                #print("Agrego %s -> %s"%(temp_k, passed))
                if recurs(dict_,goal, temp_k, passed):
                    return True

            #print("%s es una hoja"%(temp_k))            


if __name__ == "__main__":
    main()

input1.txt

M,P
P,T
P,A
A,C
T,C

input2.txt

M,A
M,B
M,C
A,G
B,C
M,P
P,D
D,H
D,F
F,T
H,D