Title
Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
Example:
Given the sorted array: [-10,-3,0,5,9],
One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:
0
/ \ -3 9 / / -10 5
有序数组变为二叉排序树，和构造二叉排序树是不太一样的撒
Solution
//cpp:
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode* f(vector<int>& nums,int l,int r){
if(l>r){
return NULL;
}
int mid=(l+r+1)/2;
TreeNode* t=new TreeNode(nums[mid]);
if(l==r){
return t;
}
t->left=f(nums,l,mid-1);
t->right=f(nums,mid+1,r);
return t;
}
TreeNode* sortedArrayToBST(vector<int>& nums) {
return f(nums,0,nums.size()-1);
}
};