108.Convert Sorted Array to Binary Search Tree

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

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#pragma once
#include<iostream>
#include<vector>
using namespace std;

struct TreeNode {
	int val;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

TreeNode *sortedArrayToBST(vector<int> &num)
{
	if (num.size() == 0)
		return NULL;
	int size = num.size();
	TreeNode* t = new TreeNode(num[size/2]);
	//参数为（begin，end）为两个迭代器，截取[begin,end)前开后闭子段为新的vector
	vector<int> n1(num.begin(), num.begin()+size/2);//前半段
	vector<int> n2(num.begin() + size / 2+1, num.end());//后半段
	t->left = sortedArrayToBST(n1);
	t->right = sortedArrayToBST(n2);
	return t;
}

void print(TreeNode* root)
{
	if (!root)
		return;
	cout << root->val << " ";
	if (root->left)
		print(root->left);
	if (root->right)
		print(root->right);
}

void main()
{
	vector<int> v = { 1, 2, 3, 4, 5, 6, 7 };
	/*vector<int> v1 = { 1 };
	vector<int> v2 = {  };
	vector<int>::iterator begain, end;

	vector<int> v3(v.begin(),v.end());
	for (int i = 0; i < v3.size(); i++)
		cout << v3[i] << ' ';*/
	print(sortedArrayToBST(v));
	system("pause");
}