LeetCode——Convert Sorted Array to Binary Search Tree

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

原题链接：https://oj.leetcode.com/problems/convert-sorted-array-to-binary-search-tree/

题目：给定一个升序排列元素的数组，将其转换成高度平衡的二叉树。

思路：已经排序，则从中间劈开，中间元素为树的根，左右递归构建。

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

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