leetcode | 95. Unique Binary Search Trees Ⅱ

題目 Given an integer n, generate all structurally unique BST’s (binary search trees) that store values 1 … n. Example: Input: 3 Output: [ [1,null,3,2], [3,2,null,1], [3,1,null,null,2], [2,1,3],

>>阅读原文<<