13 친구의 친구 찾기

def print_all_friend(g,start):
    qu=[]
    done=set()
    
    qu.append(start)
    done.add(start)
    
    while qu:
        p=qu.pop(0)
        print(p)
        for x in g[p]:
            if x not in done:
                qu.append(x)
                done.add(x)

fr_info={
    'summer':['john','justin','mike'],
    'john':['summer','justin'],
    'justin':['john','summer','mike','may'],
    'mike':['summer','justin'],
    'may':['justin','kim'],
    'kim':['may'],
    'tom':['jerry'],
    'jerry':['tom']
}

print_all_friend(fr_info,'summer')