摘要：
Given a collection of integers that might contain duplicates,nums, return all possible subsets.Note:Elements in a subset must be in non-descending ord... 阅读全文
摘要：
Givenn, how many structurally uniqueBST's(binary search trees) that store values 1...n?For example,Givenn= 3, there are a total of 5 unique BST's. 1... 阅读全文