[leetcode 108] Convert Sorted Array to Binary Search Tree

最新推荐文章于 2025-09-11 19:19:55 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。通过递归地选取中间元素作为根节点，并将其左右两侧的子数组分别构建为左子树和右子树，确保了树的高度平衡。

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

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode *sortedArrayToBST(vector<int> &num) {
        const int n = num.size();
        if (n == 0) {
            return NULL;
        }
        TreeNode *root;
        return dfs(num,0,n);
        
    }
    TreeNode *dfs(vector<int> &num, int start, int end) {
        if (start == end) {
            return NULL;
        }
        int mid = start + (end-start)/2;
        TreeNode *root = new TreeNode(num[mid]);
        root->left = dfs(num, start, mid);
        root->right = dfs(num, mid+1, end);
        return root;
    }
};