【leetcode】Convert Sorted Array to Binary Search Tree

Convert Sorted Array to Binary Search Tree

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

 

每次把中间元素当成根节点，递归即可

 

 /**
  * Definition for binary tree
  * struct TreeNode {
  *     int val;
  *     TreeNode *left;
  *     TreeNode *right;
  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
  * };
  */
 class Solution {
 public:
     TreeNode *sortedArrayToBST(vector<int> &num) {

         TreeNode *root=buildTree(num,,num.size()-);
         return root;
     }

     TreeNode *buildTree(vector<int> &num,int l,int r)
     {
         if(l>r) return NULL;

         int mid=(l+r)/;

         TreeNode *root=new TreeNode(num[mid]);
         root->left=buildTree(num,l,mid-);
         root->right=buildTree(num,mid+,r);

         return root;
     }
 };