题目: Given n, how many structurally unique BST's (binary search trees) that store values 1...n? For example, Given n = 3, there are a total of 5 unique BST's. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \ 2 1 2 3 题解: 这道题我自己是没啥思路的,感觉就是一种排列组合的计算,但是又不太会..然后…