LeetCode OJ: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.

算法思想：

每次找寻中间的元素作为父亲节点

/**
 * 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 *BST(vector
  
    &num,int start,int end){
        if(start>end)return NULL;
        int mid=(start+end)/2;
        TreeNode *head=new TreeNode(num[mid]);
        head->left=BST(num,start,mid-1);
        head->right=BST(num,mid+1,end);
        return head;
    }
    TreeNode *sortedArrayToBST(vector
   
     &num) { if(!num.size())return NULL; return BST(num,0,num.size()-1); } };