leetcode-Convert Sorted Array to Binary Search Tree（2014.4.20）

Convert Sorted Array to Binary Search Tree

  Total Accepted: 10637  Total Submissions: 33426 My Submissions

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

为保持二叉树的平衡性，鉴于数组是有序的，每一个节点都需要需要当前数组的中间节点，采用递归的方法实现。

递归尚且不够纯纯熟，还要参照别人的代码，注意下标的移动。

/**

 * 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 *BuildbBST(int left,int right,vector<int> array){

       if(left>right) return NULL;

       int mid = (left+right)/2;

       TreeNode *root = new TreeNode(array[mid]);

       if(left<right) root->left=BuildbBST(left,mid-1,array);

       if(mid<right) root->right=BuildbBST(mid+1,right,array);

       return root;

    }

    TreeNode *sortedArrayToBST(vector<int> &num) {

        int n=num.size();

     if(n==0) return NULL;

     return BuildbBST(0,n-1,num);

    }

};