算法描述：
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],
[1,null,2,null,3]
]
Explanation:
The above output corresponds to the 5 unique BST‘s shown below:
1 3 3 2 1
\ / / / \ 3 2 1 1 3 2
/ / \ 2 1 2 3
解题思路：深度优先，递归求解。
vector<TreeNode*> generateTrees(int n) { vector<TreeNode*> resuts; if(n==0) return resuts; return generate(1,n); } vector<TreeNode*> generate(int start, int end){ vector<TreeNode*> results; if(start > end){ results.push_back(nullptr); return results; } for(int i = start; i <= end; i++){ vector<TreeNode*> left = generate(start,i-1); vector<TreeNode*> right = generate(i+1,end); for(auto l:left){ for(auto r:right){ TreeNode* temp = new TreeNode(i); temp->left = l; temp->right = r; results.push_back(temp); } } } return results; }
LeetCode-95-Unique Binary Search Trees II
原文：https://www.cnblogs.com/nobodywang/p/10348481.html