文章作者:Tyan
博客:noahsnail.com ?|? CSDN ?|? 簡書
1. 問題描述
Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
2. 求解
這個題主要是根據一個有序數組構造二叉查找樹(樹的左結點小于根節點,根節點小于右結點,子樹具有同樣的性質)。構造方法主要是遞歸,每次構建子樹時都需要將數組分成左右兩半,左邊的構建左子樹,右邊的構建右子樹,中間元素構造根節點。
/**
* 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) {
return buildBinarySearchTree(nums, 0, nums.length - 1);
}
public TreeNode buildBinarySearchTree(int[] nums, int start, int end) {
if(start > end) {
return null;
}
int mid = (start + end) / 2;
TreeNode root = new TreeNode(nums[mid]);
root.left = buildBinarySearchTree(nums, start, mid - 1);
root.right = buildBinarySearchTree(nums, mid + 1, end);
return root;
}
}