108 Convert Sorted Array to Bina

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：

input：[-10,-3,0,5,9]
output：[0,-10,5,null,-3,null,9]

解释下题目：

给定一个升序的数组，构造一个平衡的二叉搜索树

1. 二分法

实际耗时：0ms

    public TreeNode sortedArrayToBST(int[] nums) {
        return recursive(nums, 0, nums.length - 1);
    }

    public TreeNode recursive(int[] nums, int low, int high) {
        if (low > high) {
            return null;
        }
        int mid = (low + high) >> 1;
        TreeNode root = new TreeNode(nums[mid]);
        root.left = recursive(nums, low, mid - 1);
        root.right = recursive(nums, mid + 1, high);
        return root;
    }

  思路就是二分法，没什么好说的

时间复杂度O(n)

空间复杂度O(n)