Leetcode108——Convert Sorted Array to Binary Search Tree

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文章作者：Tyan
博客：noahsnail.com | CSDN | 简书

1. 问题描述

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

2. 求解

这个题主要是根据一个有序数组构造二叉查找树（树的左结点小于根节点，根节点小于右结点，子树具有同样的性质）。构造方法主要是递归，每次构建子树时都需要将数组分成左右两半，左边的构建左子树，右边的构建右子树，中间元素构造根节点。

/** * 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 buildBinarySearchTree(nums, 0, nums.length - 1);    }    public TreeNode buildBinarySearchTree(int[] nums, int start, int end) {        if(start > end) {            return null;        }        int mid = (start + end) / 2;        TreeNode root = new TreeNode(nums[mid]);        root.left = buildBinarySearchTree(nums, start, mid - 1);        root.right = buildBinarySearchTree(nums, mid + 1, end);        return root;    }}

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