从北辰出发呢

同一张图，改成从北辰出发。运行下面这段程序：

NAMES = ["阿岚", "小满", "阿泰", "南风", "北辰"]
EDGES = [("阿岚", "小满"), ("阿岚", "阿泰"),
         ("小满", "阿泰"), ("阿泰", "南风")]

def build_adj():
    adj = {}
    for n in NAMES:
        adj[n] = []
    for a, b in EDGES:
        adj[a].append(b)
        adj[b].append(a)
    return adj

adj = build_adj()
seen = {"北辰": True}
q = ["北辰"]
while len(q) > 0:
    cur = q.pop(0)
    for nb in adj[cur]:
        if nb not in seen:
            seen[nb] = True
            q.append(nb)
print(len(seen))