题目描述
Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
Example:
Given the sorted array: [-10,-3,0,5,9],
One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:
0
/ \
-3 9
/ /
-10 5
题目思路
代码 C++
- 思路一、二分查找的方法构建二叉平衡树
/**
* 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.size() == 0){
return NULL;
}
return core(nums, 0, nums.size()-1);
}
TreeNode* core(vector<int>& nums, int left, int right) {
if(left <= right){
int indexOfmed = (left + right) / 2;
TreeNode* root = new TreeNode(nums[indexOfmed]);
root->left = core(nums, left, indexOfmed-1);
root->right = core(nums, indexOfmed+1, right);
return root;
}
else{
return NULL;
}
}
};
