题目链接:https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/
思路:
递归,二分确定root节点,然后确定左右子树。
AC 0ms Java:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public TreeNode sortedArrayToBST(int[] nums) {
if(nums.length==0)
return null;
TreeNode head=helper(nums,0,nums.length-1);
return head;
}
public TreeNode helper(int[] nums,int start,int end){
if(start>end)
return null;
int mid=(start+end)/2;
TreeNode root=new TreeNode(nums[mid]);
root.left=helper(nums,start,mid-1);
root.right=helper(nums,mid+1,end);
return root;
}
}