# 108. Convert Sorted Array to Binary Search Tree

## 刷题内容

• https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Example:

Given the sorted array: [-10,-3,0,5,9],

One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:

0
/ \
-3   9
/   /
-10  5


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/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode* sortedArrayToBST(vector<int>& nums) {
if(!nums.size())
return nullptr;
TreeNode* root = new TreeNode(nums[nums.size() / 2]);
vector<int> v1,v2;
if(nums.size() / 2 >= 0)
v1.assign(nums.begin(),nums.begin() + nums.size() / 2);
root ->left = sortedArrayToBST(v1);
if(nums.size() / 2 + 1 < nums.size())
v2.assign(nums.begin() + nums.size() / 2 + 1,nums.end());
root ->right = sortedArrayToBST(v2);
return root;
}
};