[leetcode] Convert Sorted Array to Binary Search Tree

Construct a balance binary search tree from a sorted array.
Recursively use the mid number as the root

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/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public TreeNode sortedArrayToBST(int[] nums) { return recur(0, nums.length-1, nums); } private TreeNode recur(int start, int end, int[] nums){ if (start > end){ return null; } int mid = (start+end)/2; TreeNode root = new TreeNode(nums[mid]); root.left = recur(start, mid-1, nums); root.right = recur(mid+1, end, nums); return root; } }