Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
divide and conquer
/**
* 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) {
if (num.empty())
return 0;
return helper(num, 0, num.size()-1);
}
TreeNode* helper(vector<int>& num, int beg, int end){
if (beg>end)
return 0;
int mid=(beg+end)/2;
TreeNode* root=new TreeNode(num[mid]);
root->left=helper(num, beg,mid-1);
root->right=helper(num,mid+1,end);
}
};