|< C++ STL Algorithm 10 | Main | C++ STL Algorithm 12 >|Site Index |Download |

MODULE 36_1

THE C++ STL ALGORITHM PART 11

template<class ForwardIterator, class Predicate> ForwardIterator remove( ForwardIterator _First,

				ForwardIterator _Last, Predicate _Pred );

// algorithm, remove_if()

#include <vector>

#include <algorithm>

#include <iostream>

using namespace std;

bool greathan(int value)

{return value >5;}

int main()

{

   vector <int> vec1;

   vector <int>::iterator Iter1, new_end;

   int i;

   for(i = 0; i <= 9; i++)

     vec1.push_back(i);

   int j;

   for(j = 0; j <= 2; j++)

     vec1.push_back(4);

   cout<<"Original vector vec1 data is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

   random_shuffle(vec1.begin(), vec1.end());

   cout<<"Random shuffle vector vec1 data is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

   // remove elements satisfying predicate greater than

   new_end = remove_if(vec1.begin(), vec1.end(), greathan);

   cout<<"Vector vec1 with elements greater than 5 removed is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

   // using erase, to change the sequence size,

   vec1.erase(new_end, vec1.end());

   cout<<"Vector vec1 resized elements greater than 5 removed is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

}

Output:

replace()

• Examines each element in a range and replaces it if it matches a specified value.

template<class ForwardIterator, class Type> void replace( ForwardIterator _First, ForwardIterator _Last,

						const Type& _OldVal, const Type& _NewVal );

Parameters

• The range referenced must be valid; all pointers must be de-referenceable and within the sequence the last position is reachable from the first by incrementation.

• The order of the elements not replaced remains stable.

• Theoperator== used to determine the equality between elements must impose an equivalence relation between its operands.

• The complexity is linear; there are (_Last – _First) comparisons for equality and at most (_Last – _First) assignments of new values.

// algorithm, replace()

#include <vector>

#include <algorithm>

#include <iostream>

using namespace std;

int main()

{

   vector <int> vec1;

   vector <int>::iterator Iter1;

   int i;

   for(i = 0; i <= 9; i++)

       vec1.push_back(i);

   int j;

   for(j = 0; j <= 2; j++)

   vec1.push_back(5);

   random_shuffle(vec1.begin(), vec1.end());

   cout<<"The original random shuffle vector vec1 data is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

       cout<<*Iter1<<" ";

   cout<<endl;

   // replace elements with other values…

   replace (vec1.begin( ), vec1.end( ), 3, 23);

   replace (vec1.begin( ), vec1.end( ), 7, 77);

   replace (vec1.begin( ), vec1.end( ), 0, 21);

   cout<<"The vector vec1 data with values replacement of 0, 3, 7 is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

       cout<<*Iter1<<" ";

   cout<<endl;

}

Output:

replace_copy()

• Examines each element in a source range and replaces it if it matches a specified value while copying the result into a new destination range.

template<class InputIterator, class OutputIterator, class Type>OutputIterator replace_copy( InputIterator _First, InputIterator _Last, OutputIterator _Result, const Type& _OldVal, const Type& _NewVal );

Parameters

• The value return is an output iterator pointing to the position one past the final element in the destination range to where the altered sequence of elements is being copied.

• The source and destination ranges referenced must not overlap and must both be valid: all pointers must be de-referenceable and within the sequences the last position is reachable from the first by incrementation.

• The order of the elements not replaced remains stable.

• Theoperator== used to determine the equality between elements must impose an equivalence relation between its operands.

• The complexity is linear: there are (_Last – _First) comparisons for equality and at most (_Last – _First) assignments of new values.

// algorithm, replace_copy()

#include <vector>

#include <list>

#include <algorithm>

#include <iostream>

using namespace std;

int main()

{

   vector <int> vec1;

   list <int> lst1 (15);

   vector <int>::iterator Iter1;

   list <int>::iterator lstIter;

   int i;

   for (i = 0; i <= 9; i++)

     vec1.push_back(i);

   int j;

   for (j = 0; j <= 3; j++)

     vec1.push_back(7);

   cout<<"The original vector vec1 data is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

   random_shuffle(vec1.begin(), vec1.end());

   int k;

   for (k = 0; k <= 15; k++)

     vec1.push_back(1);

   cout<<"The original random shuffle vector vec1 with appended data is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

   // replace elements in one part of a vector with a value of 7 with a value of 70 and copy into another part of the vector

   replace_copy(vec1.begin(), vec1.begin() + 14, vec1.end( )-15, 7, 70);

   cout<<"The vector vec1 data with a replacement value of 7 is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

   // replace elements in a vector of a value 70 with a value of 1 and copy into a list

   replace_copy(vec1.begin(), vec1.begin() + 14, lst1.begin(), 70, 1);

   cout<<"The list copy lst1 of vec1 with the value 0 replacing the 7 is:\n";

   for(lstIter = lst1.begin(); lstIter != lst1.end(); lstIter++)

      cout<<*lstIter<<" ";

   cout<<endl;

}

Output:

replace_copy_if()

• Examines each element in a source range and replaces it if it satisfies a specified predicate while copying the result into a new destination range.

template<class InputIterator, class OutputIterator, class Predicate, class Type>OutputIterator replace_copy_if( InputIterator _First, InputIterator _Last, OutputIterator _Result, Predicate _Pred, const Type& _Val );

Parameters

• The source and destination ranges referenced must not overlap and must both be valid: all pointers must be de-referenceable and within the sequences the last position is reachable from the first by incrementation.

• The order of the elements not replaced remains stable.

• Theoperator== used to determine the equality between elements must impose an equivalence relation between its operands.

• The complexity is linear; there are (_Last – _First) comparisons for equality and at most (_Last – _First) assignments of new values.

// algorithm, replace_copy_if()

#include <vector>

#include <list>

#include <algorithm>

#include <iostream>

using namespace std;

bool greaterthan(int value)

{return value > 5;}

int main()

{

   vector <int> vec1;

   list <int> lst1 (13);

   vector <int>::iterator Iter1;

   list <int>::iterator lstIter1;

   int i;

   for (i = 0; i <= 9; i++)

     vec1.push_back(i);

   int j;

   for (j = 0; j <= 3; j++)

     vec1.push_back(7);

   cout<<"The original vector vec1 data is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

       cout<<*Iter1<<" ";

   cout<<endl;

   random_shuffle(vec1.begin(), vec1.end());

   int k;

   for(k = 0; k <= 13; k++)

     vec1.push_back(3);

   cout<<"The original random shuffle vector vec1 data with appended data is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

       cout<<*Iter1<<" ";

   cout<<endl;

   // replace elements with a value of 7 in the 1st half of a vector with a value of 72 and copy it into the 2nd half of the vector

   replace_copy_if(vec1.begin(), vec1.begin() + 14, vec1.end() -14, greaterthan, 72);

   cout<<"The vector vec1 with values of 72 replacing those greater"

       <<"\n than 5 in the 1st half & copied into the 2nd half is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

   // replace elements in a vector with a value of 72 with a value of -8 and copy into a list

   replace_copy_if(vec1.begin(), vec1.begin() + 13, lst1.begin(), greaterthan, -8);

   cout<<"A list copy of vector vec1 with the value -8\n replacing "

        <<"those greater than 5 is:\n";

   for(lstIter1 = lst1.begin(); lstIter1 != lst1.end(); lstIter1++)

      cout<<*lstIter1<<" ";

   cout<<endl;

}

Output:

replace_if()

• Examines each element in a range and replaces it if it satisfies a specified predicate.

template<class ForwardIterator, class Predicate, class Type>

   void replace_if( ForwardIterator _First, ForwardIterator _Last, Predicate _Pred, const Type& _Val );

Parameters

• The range referenced must be valid; all pointers must be de-referenceable and within the sequence the last position is reachable from the first by incrementation.

• The order of the elements not replaced remains stable.

• The algorithm replace_if() is a generalization of the algorithm replace(), allowing any predicate to be specified, rather than equality to a specified constant value.

• Theoperator== used to determine the equality between elements must impose an equivalence relation between its operands.

• The complexity is linear: there are (_Last – _First) comparisons for equality and at most (_Last – _First) assignments of new values.

// algorithm, replace_if()

#include <vector>

#include <algorithm>

#include <iostream>

using namespace std;

bool greaterthan(int value)

{return value > 4;}

int main()

{

   vector <int> vec1;

   vector <int>::iterator Iter1;

   int i;

   for (i = 1; i <= 10; i++)

     vec1.push_back(i);

   int j;

   for (j = 0; j <= 2; j++)

      vec1.push_back(8);

   random_shuffle(vec1.begin(), vec1.end());

   cout<<"The original random shuffle vector vec1 data is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

   // replace elements satisfying the predicate greaterthan with a value of 21

   replace_if(vec1.begin(), vec1.end(), greaterthan, 21);

   cout<<"The vector vec1 with a value 21 replacing those\n "

       <<"elements satisfying the greater than 4 predicate is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

}

Output:

reverse()

• Reverses the order of the elements within a range.

template<class BidirectionalIterator> void reverse( BidirectionalIterator _First, BidirectionalIterator _Last );

Parameters

• The source range referenced must be valid; all pointers must be de-referenceable and within the sequence the last position is reachable from the first by incrementation.

// algorithm, reverse()

#include <vector>

#include <algorithm>

#include <iostream>

using namespace std;

int main()

{

   vector <int> vec1;

   vector <int>::iterator Iter1;

   int i;

   for(i = 11; i <= 20; i++)

      vec1.push_back(i);

   cout<<"The original vector vec1 is:\n ";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

   // reverse the elements in the vector

   reverse(vec1.begin(), vec1.end());

   cout<<"The vector vec1 data with values reversed is:\n";

   for(Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)

      cout<<*Iter1<<" ";

   cout<<endl;

}

Output:

tenouk C++ STL tutorial

Further C++ STL algorithm related reading:

1. Source code for this tutorial is available inC++ STL Algorithm source code.

2. C++ Templates programming tutorials.

3. Check thebest selling C / C++ and STL books at Amazon.com.

4. Acomplete C Standard Library.

5. Acomplete C++ Standard Library documentation that includes STL.

|< C++ STL Algorithm 10 | Main | C++ STL Algorithm 12 >|Site Index |Download |

C++ STL Algorithm Classes:  Part 1 | Part 2 |Part 3 | Part 4 | Part 5 | Part 6 | Part 7 | Part 8 |Part 9 | Part 10 |Part 11 | Part 12 | Part 13 | Part 14 | Part 15