Use sorting criterion in sort function : custom comparer « STL Algorithms Sorting « C++ Tutorial

1. C++ Tutorial
2. STL Algorithms Sorting
3. custom comparer

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */

#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>

/* PRINT_ELEMENTS()
 * - prints optional C-string optcstr followed by
 * - all elements of the collection coll
 * - separated by spaces
 */
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
    typename T::const_iterator pos;

    std::cout << optcstr;
    for (pos=coll.begin(); pos!=coll.end(); ++pos) {
        std::cout << *pos << ' ';
    }
    std::cout << std::endl;
}

/* INSERT_ELEMENTS (collection, first, last)
 * - fill values from first to last into the collection
 * - NOTE: NO half-open range
 */
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
    for (int i=first; i<=last; ++i) {
        coll.insert(coll.end(),i);
    }
}

using namespace std;

void printCollection (const list<int>& l)
{
    PRINT_ELEMENTS(l);
}

bool lessForCollection (const list<int>& l1, const list<int>& l2)
{
    return lexicographical_compare
                (l1.begin(), l1.end(),   // first range
                 l2.begin(), l2.end());  // second range
}

int main()
{
    list<int> c1, c2, c3, c4;

    // fill all collections with the same starting values
    INSERT_ELEMENTS(c1,1,5);
    c4 = c3 = c2 = c1;

    // and now some differences
    c1.push_back(7);
    c3.push_back(2);
    c3.push_back(0);
    c4.push_back(2);

    // create collection of collections
    vector<list<int> > cc;

    cc.push_back(c1);
    cc.push_back(c2);
    cc.push_back(c3);
    cc.push_back(c4);
    cc.push_back(c3);
    cc.push_back(c1);
    cc.push_back(c4);
    cc.push_back(c2);

    // print all collections
    for_each (cc.begin(), cc.end(),
              printCollection);
    cout << endl;

    // sort collection lexicographically
    sort (cc.begin(), cc.end(),    // range
          lessForCollection);      // sorting criterion

    // print all collections again
    for_each (cc.begin(), cc.end(),
              printCollection);
}

1 2 3 4 5 7
1 2 3 4 5
1 2 3 4 5 2 0
1 2 3 4 5 2
1 2 3 4 5 2 0
1 2 3 4 5 7
1 2 3 4 5 2
1 2 3 4 5

1 2 3 4 5
1 2 3 4 5
1 2 3 4 5 2
1 2 3 4 5 2
1 2 3 4 5 2 0
1 2 3 4 5 2 0
1 2 3 4 5 7
1 2 3 4 5 7