Convert Sorted Array to Binary Search Tree转换成平衡二查搜索树

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

二分递归转换

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Tree Depth-first Search

/**
* 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 *creatTree(vector<int> &num,int left,int right){
if(left>right)
return NULL;
int mid=(right+left)/2;
TreeNode *leftNode=creatTree(num,left,mid-1);
TreeNode *rightNode=creatTree(num,mid+1,right);
TreeNode *node = new TreeNode(num[mid]);
node->left=leftNode;
node->right=rightNode;
return node;
}
TreeNode *sortedArrayToBST(vector<int> &num) {
return creatTree(num,0,num.size()-1);
}
};