摘要： Symmetric TreeGiven a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric... 阅读全文

摘要： Sum Root to Leaf NumbersGiven a binary tree containing digits from0-9only, each root-to-leaf path could represent a number.An example is the root-to-l... 阅读全文

摘要： 首先呢 可能会想到用一个windows去放这些东西.可能会想到hashtable去. 但是hashtable 无法用Index去查询.abcabcbb. hashtable: abc 当第二个a来的时候, 我们想bca 貌似不好实现.这种情况就很像LRU. 用 node连接，用hashta... 阅读全文