URI: 1191 - Recuperação da Árvore

#include <iostream>

using namespace std;

struct Node {
    Node* left = NULL;
    Node* right = NULL;
    char c;
};

// Caractere atual na prefixa
string::iterator p;

Node* find(string in)
{
    if (in.length())
    {
        string str;
        str.push_back(*p);

        size_t i = in.find_first_of(str);

        if (i != string::npos)
        {
            Node* node = new Node;
            node->c = *p++;

            if (*p != '\0')
            {
                node->left = find(in.substr(0, i));
                node->right = find(in.substr(i + 1, in.length() - i));
            }

            return node;
        }
    }

    return NULL;
}

void printTree(Node* node)
{
    if (node == NULL) return;

    printTree(node->left);
    printTree(node->right);

    cout << node->c;
}

int main()
{
    string pre, in;

    while (cin >> pre >> in)
    {
        p = pre.begin();
        printTree(find(in));
        cout << endl;
    }

    return 0;
}