leetcode 108. 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: , which represents the following height balanced BST:
0
/ \
-3 9
/ /
-105
/**
* 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) {
if(nums.length == 0) return null;
int start = 0;
int end = nums.length - 1;
TreeNode node = helper(nums,start,end);
return node;
}
public TreeNode helper(int[] nums, int start, int end){
if(start > end) return null;
int mid = (start + end)/2;
TreeNode node = new TreeNode(nums);
node.left = helper(nums,start,mid-1);
node.right = helper(nums,mid+1,end);
return node;
}
}
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