C++ Tutorial/STL Algorithms Modifying sequence operations/unique — различия между версиями

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Текущая версия на 10:30, 25 мая 2010

Combine unique and erase to remove elements if there was a previous greater element

/* 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;
int main()
{
    // source data
    int source[] = { 1, 4, 4, 6, 1, 2, 2, 3, 1, 6, 6, 6, 5, 7,
                      5, 4, 4 };
    int sourceNum = sizeof(source)/sizeof(source[0]);
    list<int> coll;
    // initialize coll with elements from source
    copy (source, source+sourceNum,           // source
          coll.begin());                      // destination
    PRINT_ELEMENTS(coll);
    // remove elements if there was a previous greater element
    coll.erase (unique (coll.begin(), coll.end(),
                        greater<int>()),
                coll.end());
    PRINT_ELEMENTS(coll);
}

Use std::unique to eliminate duplicate values

#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#include <iterator>
int main()
{
   int a1[ 5 ] = { 1, 1, 1, 7, 9 };
   std::vector< int > v1( a1, a1 + 5 );
   std::ostream_iterator< int > output( cout, " " );
   std::copy( v1.begin(), v1.end(), output ); // display vector output
   // eliminate duplicate values
   std::vector< int >::iterator endLocation;
   endLocation = std::unique( v1.begin(), v1.end() );
   cout << endl;
   std::copy( v1.begin(), endLocation, output );
   return 0;
}
1 1 1 7 9
1 7 9

Use unique to remove consecutive duplicates

/* 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;
int main()
{
    // source data
    int source[] = { 1, 4, 4, 6, 1, 2, 2, 3, 1, 6, 6, 6, 5, 7,
                      5, 4, 4 };
    int sourceNum = sizeof(source)/sizeof(source[0]);
    list<int> coll;
    // initialize coll with elements from source
    copy (source, source+sourceNum,           // source
          back_inserter(coll));               // destination
    PRINT_ELEMENTS(coll);
    // remove consecutive duplicates
    list<int>::iterator pos;
    pos = unique (coll.begin(), coll.end());
    /* print elements not removed
     * - use new logical end
     */
    copy (coll.begin(), pos,                  // source
          ostream_iterator<int>(cout," "));   // destination
    cout << "\n\n";
}
1 4 4 6 1 2 2 3 1 6 6 6 5 7 5 4 4
1 4 6 1 2 3 1 6 5 7 5 4
Источник — «http://cppe.ru/index.php?title=C%2B%2B_Tutorial/STL_Algorithms_Modifying_sequence_operations/unique&oldid=2858»