题目

Leetcode 95. 不同的二叉搜索树 II

代码（9.21 首刷看解析）

class Solution {
public:vector<TreeNode*> generateTrees(int n) {return build(1,n);}vector<TreeNode*> build(int l, int r) {vector<TreeNode*> res;if(l > r) {res.emplace_back(nullptr);return res;}for(int i = l; i <= r; i++) {auto leftTree = build(l, i-1);auto rightTree = build(i+1, r);for(auto left : leftTree) {for(auto right : rightTree) {auto root = new TreeNode(i);root->left = left;root->right = right;res.emplace_back(root);}}}return res;}
};