/*

struct TreeNode {

    int val;

    struct TreeNode *left;

    struct TreeNode *right;

    TreeNode(int x) :

            val(x), left(NULL), right(NULL) {

    }

};

*/

class Solution {

public:

    TreeNode* KthNode(TreeNode* pRoot, int k){

        if(pRoot == nullptr){

            return nullptr;

        }

        stack<TreeNode*> s;

        //s.push(pRoot);

        TreeNode* p = pRoot;

        int cnt = ;

        while(!s.empty() || p != nullptr){

            while(p != nullptr){

                s.push(p);

                p = p->left;

            }

            if(!s.empty()){

                p = s.top();

                s.pop();

                ++cnt;

                if(cnt == k){

                    return p;

                }

                p = p->right;

            }

        }

        return nullptr;

    }

};