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.

这道题本质上是二分搜索+递归建立二叉树

/** * 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 *create(vector<int> &num,int begin,int end)    {        if(begin>end) return NULL;        int mid;        mid=(end+begin)/2;                TreeNode *leftNode=create(num,begin,mid-1);        TreeNode *rightNode=create(num,mid+1,end);                TreeNode *node = new TreeNode(num[mid]);                node->left=leftNode;        node->right=rightNode;                return node;    }        TreeNode *sortedArrayToBST(vector<int> &num) {        return create(num,0,num.size()-1);            }    };