108-Convert Sorted Array to Binary Search Tree

题目

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

分析

每次选择中间的那个数字

d

实现

class Solution {public:    //108. Convert Sorted Array to Binary Search Tree    TreeNode* sortedArrayToBST(vector<int>& nums) {        if (nums.size() == 0)            return NULL;        return sortedArrayToBSTHelper(nums, 0, nums.size() - 1);    }    TreeNode* sortedArrayToBSTHelper(vector<int>& nums, int start, int end)    {        TreeNode * root = NULL;        if (start <= end)        {            int index = start + (end - start) / 2;            root = new TreeNode(nums[index]);            root->left = sortedArrayToBSTHelper(nums, start, index - 1);            root->right = sortedArrayToBSTHelper(nums, index + 1, end);        }        return root;    }};