#include <string>
#include <vector>

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};

std::string
treenode_to_str(TreeNode *root)
{
    if ( root == NULL ) { return "nil"; }
    std::string ret;
    ret += "TreeNode(";
    ret += std::to_string(root->val);
    ret += ", ";
    ret += treenode_to_str(root->left);
    ret += ", ";
    ret += treenode_to_str(root->right);
    ret += ")";
    return ret;
}

template<typename T>
std::string
vector_to_str(std::vector<T> vec)
{
    std::string ret = "[";
    for ( unsigned long i = 0; i < vec.size(); ++i ) {
        if ( i == 0 ) { ret += "\""; ret += std::to_string(vec[i]); ret += "\""; continue; }
        ret += ", \""; ret += std::to_string(vec[i]); ret += "\"";
    }
    ret += "]";
    return ret;
}