108. 将有序数组转换为二叉搜索树

https://leetcode-cn.com/problems/convert-sorted-array-to-binary-search-tree/description/

package com.test;public class Lesson108 {    public static void main(String[] args) {        int[] nums = {-10,-3,0,5,9};//        int[] nums = {0,1,2,3,4,5,6,7,8};//        int[] nums = {0,1,2,3,4,5,6};        TreeNode treeNode = sortedArrayToBST(nums);        printNode(treeNode);//        TreeNode t1 = new TreeNode(1);//        TreeNode t2 = new TreeNode(2);//        TreeNode t3 = new TreeNode(3);//        t1.left = t2;//        t1.right = t3;//        printNode(t1);    }    public static TreeNode sortedArrayToBST(int[] nums) {        int length = nums.length;        TreeNode res = bst(0, length, nums);        return res;    }    private static TreeNode bst(int start, int end, int[] nums) {        // 如果有三个点        if (end - start - 3 == 0) {            TreeNode res = new TreeNode(nums[start+1]);            TreeNode left = new TreeNode(nums[start]);            TreeNode right = new TreeNode(nums[start+2]);            res.left = left;            res.right = right;            return res;        }        // 如果有两个点        if (end - start - 2 == 0) {            TreeNode res = new TreeNode(nums[start+1]);            TreeNode left = new TreeNode(nums[start]);            res.left = left;            return res;        }        // 如果有一个点        if (end - start - 1 == 0) {            TreeNode res = new TreeNode(nums[start]);            return res;        }        // 没有点        if (start - end == 0) {            return null;        }        // 如果有很多点，取中间的点作为树根，左侧的点作为左树，右侧的点作为右树        int middle = start+ (end-start)/2;        int num = nums[middle];        TreeNode res = new TreeNode(num);        TreeNode left = bst(start,middle,nums);        TreeNode right = bst(middle+1,end,nums);        res.left = left;        res.right = right;        return res;    }    private static void printNode(TreeNode treeNode) {        if (treeNode == null) {            return;        }        // 先根        System.out.print(treeNode.val+" ");        if (treeNode.left != null) {            printNode(treeNode.left);        }        // 中根//        System.out.print(treeNode.val+" ");        if (treeNode.right != null) {            printNode(treeNode.right);        }    }}