/** Definition for a binary tree node. struct TreeNode { int val; TreeNode *left; TreeNode *right; TreeNode(int x) : val(x), left(NULL), right(NULL) {} }; /class Solution {public: int kthSmallest(TreeNode* root, int k) { int res = 0; int cur = 0; mid_order(root ,cur ,res ,k); return res; } void mid...