leetcode 108 Convert Sorted Array to Binary Search Tree

原题链接：https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/

Description

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

Solution

/** * 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:    TreeNode* sortedArrayToBST(vector<int>& nums) {        int n = 0;        if(!(n = nums.size())) return nullptr;        nums.insert(nums.begin(), 0);        function<TreeNode*(int , int)> built = [&](int l, int r)->TreeNode* {            if(l > r) return nullptr;            int m = (l + r) >> 1;            TreeNode *x = new TreeNode(nums[m]);            x->left = built(l, m - 1);            x->right = built(m + 1, r);            return x;        };        return built(1, n);    }};