【leetcode】Convert Sorted Array to Binary Search Tree

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

采用二分递归。

class Solution {
public:
TreeNode *createTree(vector<int> &num,int begin,int end)
{
if(begin>end) return NULL;
int mid=(begin+end)/2;
TreeNode *root=new TreeNode(num[mid]);
root->left=createTree(num,begin,mid-1);
root->right=createTree(num,mid+1,end);
return root;
}

TreeNode *sortedArrayToBST(vector<int> &num) {
if(num.size()==0) return NULL;
return createTree(num,0,num.size()-1);
}
};