C++/STL Algorithms Modifying sequence operations/remove
Содержание
Combine remove and erase together
<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() {
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
*/ </source>
Remove all instances of "0"
<source lang="cpp">
- 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;
}
</source>
Remove an element and then erase that 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() {
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
*/ </source>
Remove copy Elements if They Meet a Criterion
<source lang="cpp">
- 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 << " ";
}
</source>
remove empty string
<source lang="cpp">
- 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);
}
</source>
Use std::remove to delete all element in a vector by value
<source lang="cpp">
- 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 */ </source>
Use the generic remove algorithm
<source lang="cpp">
- 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
*/ </source>