sorttest.cpp

Think in C++ 第二版源码

//: C21:SortTest.cpp
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
//{L} ../C20/StreamTokenizer
// Test different kinds of sorting
#include "../C20/StreamTokenizer.h"
#include "NString.h"
#include "PrintSequence.h"
#include "Generators.h"
#include "../require.h"
#include <algorithm>
#include <fstream>
#include <queue>
#include <vector>
#include <cctype>
using namespace std;

// For sorting NStrings and ignore string case:
struct NoCase {
  bool operator()(
    const NString& x, const NString& y) {
/* Somthing's wrong with this approach but I
   can't seem to see it. It would be much faster:
    const string& lv = x;
    const string& rv = y;
    int len = min(lv.size(), rv.size());
    for(int i = 0; i < len; i++)
      if(tolower(lv[i]) < tolower(rv[i]))
        return true;
    return false;
  }
*/
    // Brute force: copy, force to lowercase:
    string lv(x);
    string rv(y);
    lcase(lv);
    lcase(rv);
    return lv < rv;
  }
  void lcase(string& s) {
    int n = s.size();
    for(int i = 0; i < n; i++)
      s[i] = tolower(s[i]);
  }
};

int main(int argc, char* argv[]) {
  requireArgs(argc, 1);
  ifstream in(argv[1]);
  assure(in, argv[1]);
  StreamTokenizer words(in);
  deque<NString> nstr;
  string word;
  while((word = words.next()).size() != 0)
    nstr.push_back(NString(word));
  print(nstr);
  // Create a vector from the contents of nstr:
  vector<NString> v(nstr.begin(), nstr.end());
  sort(v.begin(), v.end());
  print(v, "sort");
  // Use an additional comparator object:
  sort(v.begin(), v.end(), NoCase());
  print(v, "sort NoCase");
  copy(nstr.begin(), nstr.end(), v.begin());
  stable_sort(v.begin(), v.end());
  print(v, "stable_sort");
  // Use an additional comparator object:
  stable_sort(v.begin(), v.end(), 
    greater<NString>());
  print(v, "stable_sort greater");
  copy(nstr.begin(), nstr.end(), v.begin());
  // Partial sorts. The additional comparator 
  // versions are obvious and not shown here.
  partial_sort(v.begin(), 
    v.begin() + v.size()/2, v.end());
  print(v, "partial_sort");
  // Create a vector with a preallocated size:
  vector<NString> v2(v.size()/2);
  partial_sort_copy(v.begin(), v.end(), 
    v2.begin(), v2.end());
  print(v2, "partial_sort_copy");
  // Finally, the weakest form of ordering:
  vector<int> v3(20);
  generate(v3.begin(), v3.end(), URandGen(50));
  print(v3, "v3 before nth_element");
  int n = 10;
  vector<int>::iterator vit = v3.begin() + n;
  nth_element(v3.begin(), vit, v3.end());
  cout << "After ordering with nth = " << n
    << ", nth element is " << v3[n] << endl;
  print(v3, "v3 after nth_element");
} ///:~