leetcode-108-Convert-Sorted-Array-to-Binary-Search-Tree

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描述

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

分析

非常简单的一道题，首先要搞清楚 BST，即二叉搜索树的概念，而给定的字符串又是排过序的，用二分法即可。

解决方案1(C++)

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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:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return arrayToBST(nums, 0, nums.size()-1);
    }
    
    TreeNode* arrayToBST(vector<int>& nums, int start, int end) {
        if(start > end) {
            return NULL;
        }
        int mid = start + (end-start)/2;
        TreeNode* root = new TreeNode(nums[mid]);
        root->left = arrayToBST(nums, start, mid-1);
        root->right = arrayToBST(nums, mid+1, end);
        return root;
    }
};

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