C++/STL Algorithms Modifying sequence operations/replace if — различия между версиями
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Текущая версия на 13:28, 25 мая 2010
Replace value equal to 70 with 42 in a deque
<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 <set>
- include <deque>
- include <algorithm>
using namespace std; /* 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;
}
int main() {
set<int,greater<int> > coll1; deque<int> coll2; // insert elements from 1 to 9 for (int i=1; i<=9; ++i) { coll1.insert(i); } PRINT_ELEMENTS(coll1,"initialized: "); // transform all elements into coll2 by multiplying 10 transform (coll1.begin(),coll1.end(), // source back_inserter(coll2), // destination bind2nd(multiplies<int>(),10)); // operation PRINT_ELEMENTS(coll2,"transformed: "); // replace value equal to 70 with 42 replace_if (coll2.begin(),coll2.end(), // range bind2nd(equal_to<int>(),70), // replace criterion 42); // new value PRINT_ELEMENTS(coll2,"replaced: ");
}
/*
initialized: 9 8 7 6 5 4 3 2 1 transformed: 90 80 70 60 50 40 30 20 10 replaced: 90 80 42 60 50 40 30 20 10
*/ </source>
std::replace_if with predicate
<source lang="cpp">
- include <iostream>
using std::cout; using std::endl;
- include <algorithm>
- include <vector>
- include <iterator>
bool greater9( int ); int main() {
int a[ 10 ] = { 10, 2, 10, 4, 16, 6, 14, 8, 12, 10 }; std::ostream_iterator< int > output( cout, " " ); std::vector< int > v3( a, a + 10 ); // copy of a cout << "Vector v3 before replacing values greater than 9:\n "; std::copy( v3.begin(), v3.end(), output ); // replace values greater than 9 in v3 with 100 std::replace_if( v3.begin(), v3.end(), greater9, 100 ); cout << "\nVector v3 after replacing all values greater" << "\nthan 9 with 100s:\n "; std::copy( v3.begin(), v3.end(), output ); cout << endl; return 0;
} bool greater9( int x ) {
return x > 9;
}
/*
Vector v3 before replacing values greater than 9:
10 2 10 4 16 6 14 8 12 10
Vector v3 after replacing all values greater than 9 with 100s:
100 2 100 4 100 6 100 8 100 100 */ </source>
Truncate numbers to fall between 0 and 255 inclusive
<source lang="cpp">
- include <algorithm>
- include <functional>
- include <iomanip>
- include <numeric>
- include <string>
- include <vector>
- include <iostream>
using namespace std; template <class T> void print(T& c){
for( typename T::iterator i = c.begin(); i != c.end(); i++ ){ std::cout << *i << endl; }
}
bool in_string( char c, const string target ){
return target.find( c ) != string::npos;
} int main( ){
vector<float> v( 5, 1 ); partial_sum( v.begin(), v.end(), v.begin() ); print( v); transform( v.begin(), v.end(), v.begin(),bind1st( multiplies<float>(), 100 ) ); v.assign( v.size(), 100 ); v[0] = -10; replace_if( v.begin(), v.end(),bind2nd( greater<float>(), 255 ), 255 ); replace_if( v.begin(), v.end(), bind2nd( less<float>(), 0 ), 0 ); print( v);
}
</source>