C++ Tutorial/STL Algorithms Modifying sequence operations/unique — различия между версиями
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Версия 14:21, 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
