108. Convert Sorted Array to Binary Search Tree
Given an integer array nums where the elements are sorted in ascending order, convert it to a height-balanced binary search tree.
A height-balanced binary tree is a binary tree in which the depth of the two subtrees of every node never differs by more than one.
Example 1:
Input: nums = [-10,-3,0,5,9]
Output: [0,-3,9,-10,null,5]
Explanation: [0,-10,5,null,-3,null,9] is also accepted:
Example 2:
Input: nums = [1,3]
Output: [3,1]
Explanation: [1,3] and [3,1] are both a height-balanced BSTs.
Constraints:
- 1 <= nums.length <= 104
- -104 <= nums[i] <= 104
- nums is sorted in a strictly increasing order.
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public TreeNode sortedArrayToBST(int[] nums) {
return buildTree(nums, 0 , nums.length-1);
}
public TreeNode buildTree(int[] nums, int low, int high){
if(low>high){
return null;
}
int mid = (low+high)/2;
TreeNode node = new TreeNode(nums[mid]);
node.left = buildTree(nums, low, mid-1);
node.right = buildTree(nums, mid+1, high);
return node;
}
}