复制链接打开自学教程
树的概念
https://www.bilibili.com/video/BV1H24y1i7bB/?spm_id_from=333.337.search-card.all.click&vd_source=29b739e23fdac2e1b84c4b96fed25972
节点、子树、边、度、高度
https://www.bilibili.com/video/BV1H24y1i7bB?p=2&vd_source=29b739e23fdac2e1b84c4b96fed25972