leetcode 108 Convert Sorted Array to Binary Search Tree

最新推荐文章于 2020-03-28 16:06:44 发布

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本文介绍了一种将已排序的数组转换为高度平衡的二叉搜索树的方法。通过递归地选择中间元素作为根节点，并递归构建左右子树，确保了树的高度平衡。这种方法适用于排序数据的快速查找。

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Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void buildTree(TreeNode *&root, vector<int> &nums, int left, int right) {
		if(left > right) {
			root = NULL;
			return;
		}

		int temp = left+(right-left+1)/2;

		root = new TreeNode(nums[temp]);

		buildTree(root->left, nums, left, temp-1);
		buildTree(root->right, nums, temp+1, right);
	}
	TreeNode *sortedArrayToBST(vector<int> &nums) {
		TreeNode *root = NULL;

		if(nums.size()==0) return root;

		buildTree(root, nums, 0, nums.size()-1);
		
		return root;
	}
};