C++ Tutorial/STL Algorithms Modifying sequence operations/unique copy

Материал из C\C++ эксперт
Перейти к: навигация, поиск

Copy only unique elements in a vector into another vector

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

  1. include <algorithm>
  2. include <vector>
  3. include <iterator>

int main() {

  const int SIZE = 10;
  int a1[ SIZE ] = { 1, 3, 5, 7, 9, 1, 3, 5, 7, 9 };
  std::vector< int > v1( a1, a1 + SIZE ); // copy of a
  std::ostream_iterator< int > output( cout, " " );
  cout << "Vector v1 contains: ";
  std::copy( v1.begin(), v1.end(), output );
  std::vector< int > results1;
  std::unique_copy( v1.begin(), v1.end(), std::back_inserter( results1 ) );
  cout << "\nAfter unique_copy results1 contains: ";
  std::copy( results1.begin(), results1.end(), output );
  return 0;

}</source>

Vector v1 contains: 1 3 5 7 9 1 3 5 7 9
After unique_copy results1 contains: 1 3 5 7 9 1 3 5 7 9

Copy standard input to standard output while compressing spaces

<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.
*/
  1. include <iostream>
  2. include <algorithm>
  3. include <iterator>

using namespace std; bool bothSpaces (char elem1, char elem2) {

   return elem1 == " " && elem2 == " ";

} int main() {

   // don"t skip leading whitespaces by default
   cin.unsetf(ios::skipws);
   /* copy standard input to standard output
    * - while compressing spaces
    */
   unique_copy(istream_iterator<char>(cin),  // beginning of source: cin
               istream_iterator<char>(),     // end of source: end-of-file
               ostream_iterator<char>(cout), // destination: cout
               bothSpaces);                  // duplicate criterion

}</source>

a
a
Terminate batch job (Y/N)? n

Read all characters while compressing whitespaces

<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.
*/
  1. include <iostream>
  2. include <string>
  3. include <algorithm>
  4. include <iterator>
  5. include <locale>

using namespace std; class bothWhiteSpaces {

 private:
   const locale& loc;    // locale
 public:
   /* constructor
    * - save the locale object
    */
   bothWhiteSpaces (const locale& l) : loc(l) {
   }
   /* function call
    * - returns whether both characters are whitespaces
    */
   bool operator() (char elem1, char elem2) {
       return isspace(elem1,loc) && isspace(elem2,loc);
   }

}; int main() {

   string contents;
   // don"t skip leading whitespaces
   cin.unsetf (ios::skipws);
   //Read all characters while compressing whitespaces
   unique_copy(istream_iterator<char>(cin),    // beginning of source
               istream_iterator<char>(),       // end of source
               back_inserter(contents),        // destination
               bothWhiteSpaces(cin.getloc())); // criterion for removing
   // process contents
   // - here: write it to the standard output
   cout << contents;

}</source>

string
string
asdf

string
string
asdf
Terminate batch job (Y/N)? n

Remove adjacent duplicates: unique_copy

<source lang="cpp">#include <string>

  1. include <iostream>
  2. include <algorithm>

using namespace std; int main() {

   const string hello("Hello, how are you?");
   string s(hello.begin(),hello.end());
   // iterate through all of the characters
   string::iterator pos;
   for (pos = s.begin(); pos != s.end(); ++pos) {
       cout << *pos;
   }
   cout << endl;
   /* remove adjacent duplicates
    * - unique() reorders and returns new end
    * - erase() shrinks accordingly
    */
   s.erase (unique(s.begin(), s.end()),  s.end());
   cout << "no duplicates: " << s << endl;

}</source>

Hello, how are you?
no duplicates: Helo, how are you?

Use unique_copy to copy elements in an array to list with back_inserter

<source lang="cpp">#include <iostream>

  1. include <list>
  2. include <algorithm>
  3. include <string>

using namespace std; int main( ) {

  string arrStr[5] = {"A", "B", "A", "D", "E"};
  list<string> lstStrDest;
  unique_copy(&arrStr[0], &arrStr[5], back_inserter(lstStrDest));
  for (list<string>::iterator p = lstStrDest.begin( );
       p != lstStrDest.end( ); ++p) {
     cout << *p << endl;
  }

}</source>

A
B
A
D
E

Use unique_copy to print elements with consecutive duplicates removed

<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.
*/
  1. include <iostream>
  2. include <vector>
  3. include <deque>
  4. include <list>
  5. include <set>
  6. include <map>
  7. include <string>
  8. include <algorithm>
  9. include <iterator>
  10. include <functional>
  11. 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; bool differenceOne (int elem1, int elem2) {

   return elem1 + 1 == elem2 || elem1 - 1 == elem2;

} 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]);
   // initialize coll with elements from source
   list<int> coll;
   copy(source, source+sourceNum,      // source
        back_inserter(coll));          // destination
   PRINT_ELEMENTS(coll);
   // print elements with consecutive duplicates removed
   unique_copy(coll.begin(), coll.end(),          // source
               ostream_iterator<int>(cout," "));  // destination
   cout << endl;

}</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

Use unique_copy to print elements without consecutive entries that differ by one

<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.
*/
  1. include <iostream>
  2. include <vector>
  3. include <deque>
  4. include <list>
  5. include <set>
  6. include <map>
  7. include <string>
  8. include <algorithm>
  9. include <iterator>
  10. include <functional>
  11. 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; bool differenceOne (int elem1, int elem2) {

   return elem1 + 1 == elem2 || elem1 - 1 == elem2;

} 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]);
   // initialize coll with elements from source
   list<int> coll;
   copy(source, source+sourceNum,      // source
        back_inserter(coll));          // destination
   PRINT_ELEMENTS(coll);
   // print elements without consecutive entries that differ by one
   unique_copy(coll.begin(), coll.end(),         // source
               ostream_iterator<int>(cout," "),  // destination
               differenceOne);                   // duplicates criterion
   cout << endl;

}</source>

1 4 4 6 1 2 2 3 1 6 6 6 5 7 5 4 4
1 4 4 6 1 3 1 6 6 6 4 4