方法1:递归
时间复杂度:$O(n)$
空间复杂度:$O(logn)$
解题思路
递归地取中间值作为树的根节点。
Java 代码
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public TreeNode sortedArrayToBST(int[] nums) {
return constructor(nums,0, nums.length - 1);
}
public TreeNode constructor(int[] nums, int left, int right) {
if (left > right) return null;
int mid = left + ((right - left) >> 1);
TreeNode root = new TreeNode(nums[mid]);
root.left = constructor(nums, left, mid - 1);
root.right = constructor(nums, mid + 1, right);
return root;
}
}