lintcode-177-把排序数组转换为高度最小的二叉搜索树

177-把排序数组转换为高度最小的二叉搜索树

给一个排序数组（从小到大），将其转换为一棵高度最小的排序二叉树。

注意事项

There may exist multiple valid solutions, return any of them.

样例

给出数组 [1,2,3,4,5,6,7], 返回

标签

递归 二叉树 Cracking The Coding Interview

思路

code

/**
* Definition of TreeNode:
* class TreeNode {
* public:
*     int val;
*     TreeNode *left, *right;
*     TreeNode(int val) {
*         this->val = val;
*         this->left = this->right = NULL;
*     }
* }
*/
class Solution {
public:
/**
* @param A: A sorted (increasing order) array
* @return: A tree node
*/
TreeNode *sortedArrayToBST(vector<int> &A) {
// write your code here
int size = A.size();
if (size <= 0) {
return nullptr;
}
TreeNode *root;
root = sortedArrayToBST(A, 0, size-1);
return root;
}
TreeNode * sortedArrayToBST(vector<int> &A,  int low, int high) {
if (low <= high) {
int mid = low + (high - low) / 2;
TreeNode * root = new TreeNode(A[mid]);
root->left = sortedArrayToBST(A, low, mid - 1);
root->right = sortedArrayToBST(A, mid + 1, high);
return root;
}
else {
return nullptr;
}
}
};