C++/STL Algorithms Modifying sequence operations/fill — различия между версиями
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Текущая версия на 10:28, 25 мая 2010
Содержание
Use fill function to overwrite all elements with "again"
/* 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()
{
// print ten times 7.7
fill_n(ostream_iterator<float>(cout, " "), // beginning of destination
10, // count
7.7); // new value
cout << endl;
list<string> coll;
// insert "hello" nine times
fill_n(back_inserter(coll), // beginning of destination
9, // count
"hello"); // new value
// overwrite all elements with "again"
fill(coll.begin(), coll.end(), // destination
"again"); // new value
PRINT_ELEMENTS(coll,"coll: ");
}
/*
7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7
coll: again again again again again again again again again
*/
Use fill function to replace the second and up to the last element but one with "hmmm"
/* 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()
{
// print ten times 7.7
fill_n(ostream_iterator<float>(cout, " "), // beginning of destination
10, // count
7.7); // new value
cout << endl;
list<string> coll;
// insert "hello" nine times
fill_n(back_inserter(coll), // beginning of destination
9, // count
"hello"); // new value
// replace the second and up to the last element but one with "hmmm"
list<string>::iterator pos1, pos2;
pos1 = coll.begin();
pos2 = coll.end();
fill (++pos1, --pos2, // destination
"hmmm"); // new value
PRINT_ELEMENTS(coll,"coll: ");
}
/*
7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7
coll: hello hmmm hmmm hmmm hmmm hmmm hmmm hmmm hello
*/
Use std::fill to fill vector with chars
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm> // algorithm definitions
#include <vector> // vector class-template definition
#include <iterator> // ostream_iterator
int main()
{
std::vector< char > chars( 10 );
std::ostream_iterator< char > output( cout, " " );
std::fill( chars.begin(), chars.end(), "5" ); // fill chars with 5s
cout << "Vector chars after filling with 5s:\n";
std::copy( chars.begin(), chars.end(), output );
cout << endl;
return 0;
}
/*
Vector chars after filling with 5s:
5 5 5 5 5 5 5 5 5 5
*/
Use the generic fill algorithms: Fill first 5 positions of vector1 with X"s
#include <iostream>
#include <cassert>
#include <algorithm>
#include <vector>
#include <string>
using namespace std;
int main()
{
string s("Hello there");
vector<char> vector1(s.begin(), s.end());
// Fill first 5 positions of vector1 with X"s:
fill(vector1.begin(), vector1.begin() + 5, "X");
vector<char>::iterator pos;
for (pos=vector1.begin(); pos!=vector1.end(); ++pos) {
cout << *pos << " ";
}
return 0;
}
/*
X X X X X t h e r e
*/