class Solution {

 public:

     TreeNode* KthNode(TreeNode* pRoot, int k)

     {

         int i=INT32_MIN;

         return func(pRoot,k,i);

     }

     TreeNode* func(TreeNode* node,int k,int& i){

         if(node==nullptr){

             if(i==INT32_MIN){

                 i=;

             }

             return nullptr;

         }

         decltype(node) t;

         if(t=func(node->left,k,i)){

             return t;

         }

         ++i;

         if(i==k){

             return node;

         }

         if(t=func(node->right,k,i)){

             return t;

         }

         return nullptr;

     }

 };