C++/STL Algorithms Sorting/custom comparer

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Sort objects stored in deque

 
 
/* 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 <string>
#include <deque>
#include <set>
#include <algorithm>
using namespace std;

/* class Person
 */
class Person {
  private:
    string fn;    // first name
    string ln;    // last name
  public:
    Person() {
    }
    Person(const string& f, const string& n)
     : fn(f), ln(n) {
    }
    string firstname() const;
    string lastname() const;
    // ...
};
inline string Person::firstname() const {
    return fn;
}
inline string Person::lastname() const {
    return ln;
}
ostream& operator<< (ostream& s, const Person& p)
{
    s << "[" << p.firstname() << " " << p.lastname() << "]";
    return s;
}

/* binary function predicate:
 * - returns whether a person is less than another person
 */
bool personSortCriterion (const Person& p1, const Person& p2)
{
    /* a person is less than another person
     * - if the last name is less
     * - if the last name is equal and the first name is less
     */
    return p1.lastname()<p2.lastname() ||
           (p1.lastname()==p2.lastname() &&
            p1.firstname()<p2.firstname());
}
int main()
{
    // create some persons
    Person p1("nicolai","josuttis");
    Person p2("ulli","josuttis");
    Person p3("anica","josuttis");
    Person p4("lucas","josuttis");
    Person p5("lucas","otto");
    Person p6("lucas","arm");
    Person p7("anica","holle");
    
    // insert person into collection coll
    deque<Person> coll;
    coll.push_back(p1);
    coll.push_back(p2);
    coll.push_back(p3);
    coll.push_back(p4);
    coll.push_back(p5);
    coll.push_back(p6);
    coll.push_back(p7);
    // print elements
    cout << "deque before sort():" << endl;
    deque<Person>::iterator pos;
    for (pos = coll.begin(); pos != coll.end(); ++pos) {
        cout << *pos << endl;
    }
    // sort elements
    sort(coll.begin(),coll.end(),    // range
         personSortCriterion);       // sort criterion
    // print elements
    cout << "deque after sort():" << endl;
    for (pos = coll.begin(); pos != coll.end(); ++pos) {
        cout << *pos << endl;
    }
}
/* 
deque before sort():
[nicolai josuttis]
[ulli josuttis]
[anica josuttis]
[lucas josuttis]
[lucas otto]
[lucas arm]
[anica holle]
deque after sort():
[lucas arm]
[anica holle]
[anica josuttis]
[lucas josuttis]
[nicolai josuttis]
[ulli josuttis]
[lucas otto]
 */


Use sorting criterion in sort function

 
 
/* 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
 */