将有序数组转化为二叉搜索树
(题目链接)[]https://leetcode-cn.com/problems/convert-sorted-array-to-binary-search-tree/]
/**
* 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 solve(nums,0,nums.length - 1);
}
public TreeNode solve(int[] nums,int l,int r){
if(l > r){
return null;
}
int mid = r - ((r - l) / 2);
TreeNode root = new TreeNode(nums[mid]);
root.left = solve(nums,l,mid - 1);
root.right = solve(nums,mid + 1,r);
return root;
}
}
数组是有序的,为了构造平衡二叉树,我们每次都取中间的数作为root结点的值