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  • [LC] 108. Convert Sorted Array to Binary Search Tree

    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

    /**
     * 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 buildBST(0, nums.length - 1, nums);
        }
        
        private TreeNode buildBST(int start, int end, int[] nums) {
            if (start > end) {
                return null;
            }
            int mid = start + (end - start) / 2;
            TreeNode cur = new TreeNode(nums[mid]);
            cur.left = buildBST(start, mid - 1, nums);
            cur.right = buildBST(mid + 1, end, nums);
            return cur;
        }
    }
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  • 原文地址:https://www.cnblogs.com/xuanlu/p/12170624.html
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