TreeNode* Create_Tree(vector<int> &nums, int i) //层次遍历创建二叉树
{
    if (i >= nums.size() || nums[i] == NULL ) //超出数组范围
        return nullptr;
    TreeNode *root = new TreeNode(nums[i]);
    root->left = Create_Tree(nums, i * 2);
    root->right = Create_Tree(nums, i * 2 + 1);

    return root;
}

int main()
{
    /*二叉树
        1
       / \
      3   2
     /\    \
    4  5    9
    */
    vector<int> nums = {1, 3, 2, 4, 5, 0, 9};  //层次数组
    nums.insert(nums.begin(), NULL);  //头部插入一个占位的, 方便下标从1开始

    TreeNode *tree = Create_Tree(nums, 1);  //从下标1开始用，层次遍历值创建二叉树

    nums.erase(nums.begin(), nums.begin() + 1); //删除头部的0