C++/STL Algorithms Modifying sequence operations/remove
Содержание
Combine remove and erase together
/* 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()
{
vector<int> coll;
INSERT_ELEMENTS(coll,2,6);
INSERT_ELEMENTS(coll,4,9);
INSERT_ELEMENTS(coll,1,7);
PRINT_ELEMENTS(coll,"coll: ");
// remove all elements with value 5
vector<int>::iterator pos;
// remove all elements less than 4
coll.erase(remove_if(coll.begin(), coll.end(), // range
bind2nd(less<int>(),4)), // remove criterion
coll.end());
PRINT_ELEMENTS(coll,"<4 removed: ");
}
/*
coll: 2 3 4 5 6 4 5 6 7 8 9 1 2 3 4 5 6 7
<4 removed: 4 5 6 4 5 6 7 8 9 4 5 6 7
*/
Remove all instances of "0"
#include <algorithm>
#include <vector>
#include <list>
#include <iostream>
using namespace std;
int main (){
list <int> l;
for (int nCount = 0; nCount < 10; ++ nCount)
l.push_back (nCount);
list <int>::const_iterator li;
for ( li = l.begin (); li != l.end (); ++ li )
cout << *li << " ";
vector <int> v (l.size () * 2);
vector <int>::iterator iLastPos;
iLastPos = copy ( l.begin (), l.end (), v.begin () );
vector <int>::iterator i;
i = remove (v.begin (), v.end (), 0);
// Use this new "end position" to resize vector
v.erase (i, v.end ());
return 0;
}
Remove an element and then erase that 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()
{
vector<int> coll;
INSERT_ELEMENTS(coll,2,6);
INSERT_ELEMENTS(coll,4,9);
INSERT_ELEMENTS(coll,1,7);
PRINT_ELEMENTS(coll,"coll: ");
// remove all elements with value 5
vector<int>::iterator pos;
pos = remove(coll.begin(), coll.end(), // range
5); // value to remove
PRINT_ELEMENTS(coll,"size not changed: ");
// erase the ""removed"" elements in the container
coll.erase(pos, coll.end());
PRINT_ELEMENTS(coll,"size changed: ");
}
/*
coll: 2 3 4 5 6 4 5 6 7 8 9 1 2 3 4 5 6 7
size not changed: 2 3 4 6 4 6 7 8 9 1 2 3 4 6 7 5 6 7
size changed: 2 3 4 6 4 6 7 8 9 1 2 3 4 6 7
*/
Remove copy Elements if They Meet a Criterion
#include <algorithm>
#include <functional>
#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;
}
}
template<class InputIterator, class OutputIterator, class Predicate >
OutputIterator copy_if( InputIterator start, InputIterator stop,OutputIterator out, Predicate select ){
while( start != stop ){
if( select( *start ) )
*out++ = *start;
++start;
}
return out;
}
int main( )
{
const int numbers = 7;
const int num[numbers] = { -5, 0, 13, 20, 10, 4, -1 };
vector<int> v1( num, num+numbers );
print( v1 );
vector<int> v2( num, num+numbers );
vector<int>::const_iterator v2_copy_end = remove_copy_if( v1.begin(), v1.end(), v2.begin(),not1( bind2nd( greater<int>(), 10 ) ) );
for( vector<int>::const_iterator i = v2.begin(); i != v2_copy_end;++i )
cout << *i << " ";
}
remove empty string
#include <functional>
#include <algorithm>
#include <string>
#include <vector>
#include <iostream>
using namespace std;
void removeEmptyStrings(vector<string>& strings)
{
vector<string>::iterator it = remove_if(strings.begin(), strings.end(),mem_fun_ref(&string::empty));
// erase the removed elements
strings.erase(it, strings.end());
}
void printString(const string& str)
{
cout << str << " ";
}
int main(int argc, char** argv)
{
vector<string> myVector;
myVector.push_back("A");
myVector.push_back("B");
myVector.push_back("C");
myVector.push_back("D");
myVector.push_back("E");
myVector.push_back("F");
removeEmptyStrings(myVector);
cout << "Size is " << myVector.size() << endl;
for_each(myVector.begin(), myVector.end(), &printString);
cout << endl;
return (0);
}
Use std::remove to delete all element in a vector by value
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#include <iterator>
int main()
{
int a[ 10 ] = { 10, 2, 10, 4, 16, 6, 14, 8, 12, 10 };
std::ostream_iterator< int > output( cout, " " );
std::vector< int > v( a, a + 10 ); // copy of a
std::vector< int >::iterator newLastElement;
cout << "Vector v before removing all 10s:\n ";
std::copy( v.begin(), v.end(), output );
// remove all 10s from v
newLastElement = std::remove( v.begin(), v.end(), 10 );
cout << "\nVector v after removing all 10s:\n ";
std::copy( v.begin(), newLastElement, output );
return 0;
}
/*
Vector v before removing all 10s:
10 2 10 4 16 6 14 8 12 10
Vector v after removing all 10s:
2 4 16 6 14 8 12
*/
Use the generic remove algorithm
#include <iostream>
#include <cassert>
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
const int N = 11;
int array1[N] = {1, 2, 0, 3, 4, 0, 5, 6, 7, 0, 8};
vector<int> vector1;
for (int i = 0; i < N; ++i)
vector1.push_back(array1[i]);
// Remove the zeros from vector1:
vector<int>::iterator new_end;
new_end = remove(vector1.begin(), vector1.end(), 0);
for (int i = 0; i < (int)vector1.size(); ++i)
cout << vector1[i];
cout << "\n\n\n\n\n";
// The size of vector1 remains the same:
assert (vector1.size() == N);
cout << vector1.size();
cout << "\n\n\n\n\n";
// The nonzero elements are left in [vector1.begin(), new_end). Erase the rest:
vector1.erase(new_end, vector1.end());
// Show that 3 elements were removed and the nonzero elements remain, in their original order:
assert (vector1.size() == N - 3);
cout << vector1.size();
cout << "\n\n\n\n\n";
for (int i = 0; i < (int)vector1.size(); ++i)
cout << vector1[i];
return 0;
}
/*
12345678708
11
8
12345678
*/