摘要： You need to construct a string consists of parenthesis and integers from a binary tree with the preorder traversing way. The null node needs to be rep 阅读全文

摘要： Given a group of two strings, you need to find the longest uncommon subsequence of this group of two strings. The longest uncommon subsequence is defi 阅读全文

摘要： Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array. Example 1: Input: 3 / \ 9 20 / \ 15 7 Outp 阅读全文