LeetCode（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

给定一个有序序列，构造一颗平衡的二叉查找树。

思想：序列中值构造根节点，递归，前半序列构造左子树，有伴序列构造右子树。

AC代码

/**
* 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) {
if (nums.empty())
return NULL;

else
return make(nums.begin(), nums.end());

}

template <typename Iter>
TreeNode *make(Iter beg, Iter end)
{
if (beg == end)
return NULL;

//求元素节点个数
int size = end - beg;

TreeNode *root = new TreeNode(*(beg + size / 2));

root->left = make(beg, beg + size / 2);
root->right = make(beg + size / 2 + 1, end);
return root;
}
};

GitHub测试程序源码