LeetCode(108) Convert Sorted Array to Binary Search Tree解题报告

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

解题思路:

取数组中点mid作为根节点，从start到mid-1作为左子树，mid+1到end作为右子树，递归调用即可。

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