python 利用列表的浅拷贝(不用递归)实现递归效果, 生成层级菜单建树数据

import time

def build_tree_c(data):
    """建树:找儿子算法
    1万层节点耗时(秒):7.0288989543914795
    """
    for index, i in enumerate(data):
        for j in data:
            if i["id"]==j["parentId"]:
                if "children" not in data[index].keys():
                    data[index]["children"] = []
                data[index]["children"].append(j)

    res = [i for i in data if i["parentId"]==0]
    return res


def build_tree_p(data):
	"""建树:找爸爸算法
	1万层节点耗时(秒):0.005019187927246094
	"""
	# 建立一个 id 对 index 的字典
	res = []
	c_dict ={}
	for index, i in enumerate(data):
		c_dict[i["id"]] = index

	# 用本节点的 parentId 通过字典找到父节点的index
	for i in data:
		if i['parentId'] == 0:
			res.append(i)
		else:
			papa = data[c_dict[i["parentId"]]]
			if "children" not in papa.keys():
				papa["children"] = []
			papa["children"].append(i)

	# res = [i for i in data if i["parentId"]==0]
	return res


# 创建一个1万个节点: [{'id': 0, 'parentId': 1}, {'id': 1, 'parentId': 2}, {'id': 2, 'parentId': 3}, ...{'id': 9999, 'parentId': 10000}]
data = [{"id": i+1,"parentId": i} for i in range(10000)]

# 将这1万个节点建树:
t1 = time.time()
res = build_tree_p(data)
# res = build_tree_c(data)
t2 = time.time()
st = t2-t1

print("Start time:\t%s\nStop time:\t%s\nElapsed time:\t%s" % (t1, t2, st))