【树】面试题 04.02. 最小高度树

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12      TreeNode* dfs(const vector<int> &nums, int L, int R) 
13      {
14         if(L > R) 
15         {
16             return nullptr;
17         }
18         int mid = (L+R)>>1;
19         auto ptr = new TreeNode(nums[mid]); //填充根节点
20         ptr->left = dfs(nums, L, mid-1); //构造左子树
21         ptr->right = dfs(nums, mid+1, R); //构造右子树
22         return ptr;
23     }
24     TreeNode* sortedArrayToBST(vector<int>& nums) 
25     {
26         return dfs(nums, 0, nums.size()-1);
27     }
28 };