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.
您在真实的面试中是否遇到过这个题？
Yes
样例
给出数组 [1,2,3,4,5,6,7], 返回
4
/ \
2 6
/ \ / \
1 3 5 7/**
* 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 len=A.size();
if(len==0)
return NULL;
return build(A,0,len-1);
}
TreeNode *build(vector<int> &A,int s,int e)
{
if(s>e)
return NULL;
int m=(s+e)>>1;
TreeNode *q=new TreeNode(A[m]);
q->left=build(A,s,m-1);
q->right=build(A,m+1,e);
return q;
}
};