/* Code for exercise 7.7. |  | "C++ Solutions--Companion to The C++ Programming Language, Third Edition" | by David Vandevoorde; Addison-Wesley 1998; ISBN 0-201-30965-3. | | Permission to use, copy, modify, distribute and sell this software | and its documentation for any purpose is hereby granted without fee. | The author makes no representations about the suitability of this | software for any purpose.  It is provided "as is" without express or | implied warranty. `----------------------------------------------------------------------*/#include <iostream>#include <string>struct Tnode {   std::string word;   int count;   Tnode *left;   Tnode *right;};Tnode* new_Tnode(std::string const &word) {   Tnode *node = new Tnode;   node->word = word;   node->count = 1;   node->left = node->right = 0;   return node;}void enter_word(Tnode *&root, std::string const &word) {   if (root!=0) {      // First search for the node in the tree:      Tnode *node = root;      while (1) {         int order = word.compare(node->word);         if (order==0) { // Word is in the tree already            ++node->count;            break;         } else {            Tnode *&next = order<0? node->left                                  : node->right;            if (next==0) { // Word not yet in tree?               next = new_Tnode(word);               break;            } else               node = next;         }      }   } else { // Create the first node at the root      root = new_Tnode(word);   }}void write(std::ostream &output, Tnode *node,           bool indent, int spaces = 2) {   if (node) {      write(output, node->left, indent, spaces+2);      if (indent)         for (int k = 0; k!=spaces; ++k)            cout << ' ';      output << node->word             << " (" << node->count << ")\n";      write(output, node->right, indent, spaces+2);   }}int main() {   std::cout << "Enter words terminated by \"$done\"\n";   Tnode *tree;   while (1) {      std::string word;      std::cin >> word;      if (word=="$done") {         break;      }      enter_word(tree, word);   }   write(std::cout, tree, true /* do indent */);   return 0;}