摘要：
Given a binary tree, flatten it to a linked list in-place. （Medium） For example,Given The flattened tree should look like: 分析： 将树的问题和链表插入问题结合。对于每个节点，寻 阅读全文
摘要：
Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.（Medium） For example:Given the below binary tree 阅读全文