/* Code for exercise 18.19. |  | "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 <algorithm>#include <ctime>#include <fstream>#include <functional>#include <iostream>#include <list>#include <string>#include <vector>void error(char const *name, char const *msg) {   std::cerr << name << msg << '\n';   std::exit(1);}// The following is copied from Exercise 18.5:template<class T, class Less, class Cursor>void quicksort(Less fcn, Cursor left, Cursor right) {   // Zero- or one-element lists are trivially sorted:   Cursor probe = left;   if (probe==right or ++probe==right)      return;   T pivot = *left;   // Partition the list into elements less-than and not   // less-than the pivot (less-than is defined by fcn):   Cursor p = partition(left, right, bind2nd(fcn, pivot));   if (p==left)      ++p;   else   if (p==right)      --p;   // Recursively sort these partitions:   quicksort<T>(fcn, left, p);   quicksort<T>(fcn, p, right);}void test_quicksort(char *filename) {   std::ifstream in(filename);   std::list<std::string> words;   std::string word;   while (in >> word)      words.push_back(word);   std::clock_t start = std::clock();   quicksort<std::string>(std::less<std::string>(), words.begin(), words.end());   std::cerr << "QuickSort: "             << (std::clock()-start)/CLOCKS_PER_SEC << '\n';}void test_copysort(char *filename) {   using std::string;   std::ifstream in(filename);   std::list<string> words;   string word;   while (in >> word)      words.push_back(word);   std::clock_t start = std::clock();   std::vector<string> tmp(words.size(), string());   std::copy(words.begin(), words.end(), tmp.begin());   std::sort(tmp.begin(), tmp.end(), std::less<string>());   std::copy(tmp.begin(), tmp.end(), words.begin());   std::cerr << "Copy+Sort: "             << (std::clock()-start)/CLOCKS_PER_SEC << '\n';}int main(int argc, char *argv[]) {   if (argc!=2)      error(argv[0], ": unexpected number of arguments.\n");   test_quicksort(argv[1]);   test_copysort(argv[1]);   return 0;}