1 class Solution { 2 public: 3 int rank; 4 int result; 5 6 void help(TreeNode* root, int k){ 7 if(!root) return; 8 9 help(root->left, k); 10 if(++rank == k){ 11 result = root->val; 12 return; 13 } 14 help(root->right, k); 15 } 16 int kthSmallest(TreeNode* ...