Convert Sorted Array to Binary Search Tree
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
class Solution {
public TreeNode helper(int[] nums, int start, int end) {
if (start > end)
return null;
int mid = start + (end - start) / 2;
TreeNode ans = new TreeNode(nums[mid]);
ans.left = helper(nums, start, mid - 1);
ans.right = helper(nums, mid + 1, end);
return ans;
}
public TreeNode sortedArrayToBST(int[] nums) {
return helper(nums, 0, nums.length - 1);
}
}
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