C++ Tutorial/STL Algorithms Modifying sequence operations/unique — различия между версиями
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Версия 17:21, 25 мая 2010
Combine unique and erase to remove elements if there was a previous greater element
<source lang="cpp">/* 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);
}</source>
Use std::unique to eliminate duplicate values
<source lang="cpp">#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;
}</source>
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Use unique to remove consecutive duplicates
<source lang="cpp">/* 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";
}</source>
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