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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
题目大意:
给出一个有序数组,我们需要计算出一颗高度平衡的BST。每个节点的左右子树上的节点数不超过1。
解题思路:
找出左右子树的中心点mid即可 mid=(r+l+1)/2
其结果答案不唯一。
/**
* 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 {
private:
TreeNode* dfs(vector<int>& nums, int left, int right){
if(left == right){
TreeNode *tmp = new TreeNode(nums[left]);
return tmp;
}else if(left>right){
return nullptr;
}
int mid = (right + left + 1)/2;
TreeNode *root = new TreeNode(nums[mid]);
root->left = dfs(nums, left, mid-1);
root->right = dfs(nums, mid+1, right);
return root;
}
public:
TreeNode* sortedArrayToBST(vector<int>& nums) {
return dfs(nums, 0, nums.size()-1);
}
};