Given an array where elements are sorted in ascending order, convert it to a height balanced BST. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1. Example: Given the sorted array: [-10,-3,0,5,9], One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST: 0 / -3 9 / / -10 5
题目需要构建height-balanced BST, 应该能想到找到中间的点，然后构造，构造的时候用DFS
/**
* 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 == null || nums.length == 0) {
return null;
}
return buildTree(0, nums.length-1, nums);
}
public TreeNode buildTree(int low, int high, int[] nums) {
if (low > high) {
return null;
}
int mid = low + (high - low)/2;
TreeNode treeNode = new TreeNode(nums[mid]);
treeNode.left = buildTree(low, mid-1, nums);
treeNode.right = buildTree(mid+1, high, nums);
return treeNode;
}
}
LeetCode - Convert Sorted Array to Binary Search Tree
原文：https://www.cnblogs.com/incrediblechangshuo/p/11670186.html