Sword refers to Offer 54. The k-th largest node of the binary search tree

Here is what cross-binary search tree (ordered

if its left subtree is not empty, the value of all nodes on the left subtree is less than its root The value of the node;

if its right subtree is not empty, the values of all nodes on the right subtree are greater than the value of its root node;

its left and right subtrees are also binary sorted trees,

so it is In-order traversal

```
class Solution {
public:
int kthLargest(TreeNode* root, int k) {
vector<int>res;
digui(root,res);
reverse(res.begin(),res.end());
return res[k-1];
}
void digui(TreeNode*root,vector<int>&res)
{
if(!root) return;
digui(root->left,res);
res.push_back(root->val);
digui(root->right,res);
}
};
```