【leetcode】数组建树

108. 将有序数组转换为二叉搜索树

class Solution {
public:   
 TreeNode* sortedArrayToBST(vector<int>& nums) {        return build(nums, 0, nums.size() - 1);   
 }   
 TreeNode* build(vector<int>& nums,int l,int r) {        if(l > r)  
  return NULL;  
 int mid = l + (r - l) / 2;    
 TreeNode* root = new TreeNode(nums[mid]);        root->left  = build(nums, l, mid - 1);   
 root->right = build(nums, mid + 1, r);   
  return root;  
  }
 };