C++ Tutorial/STL Algorithms Modifying sequence operations/replace

Replace values in vector with another value with replace()

<source lang="cpp">#include <iostream>

1. include <algorithm>
2. include <vector>

using namespace std; bool greater9( int ); int main() {

  const int SIZE = 10;
  int a[ SIZE ] = { 10, 2, 10, 4, 16, 6, 14, 8, 12, 10 };
  // Replace 10s in v1 with 100
  vector< int > v1( a, a + SIZE );
  replace( v1.begin(), v1.end(), 10, 100 );
  return 0;

} bool greater9( int x ){

  return x > 9;

}</source>

Use replace to replace all elements with value 6 with 42

<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.
*/

1. include <iostream>
2. include <vector>
3. include <deque>
4. include <list>
5. include <set>
6. include <map>
7. include <string>
8. include <algorithm>
9. include <iterator>
10. include <functional>
11. 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() {

   list<int> coll;
   INSERT_ELEMENTS(coll,2,7);
   INSERT_ELEMENTS(coll,4,9);
   PRINT_ELEMENTS(coll,"coll: ");
   // replace all elements with value 6 with 42
   replace (coll.begin(), coll.end(),     // range
            6,                            // old value
            42);                          // new value
   PRINT_ELEMENTS(coll,"coll: ");

}</source>

coll: 2 3 4 5 6 7 4 5 6 7 8 9
coll: 2 3 4 5 42 7 4 5 42 7 8 9

Use replace to replace all elements with value less than 5 with 0

<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.
*/

1. include <iostream>
2. include <vector>
3. include <deque>
4. include <list>
5. include <set>
6. include <map>
7. include <string>
8. include <algorithm>
9. include <iterator>
10. include <functional>
11. 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() {

   list<int> coll;
   INSERT_ELEMENTS(coll,2,7);
   INSERT_ELEMENTS(coll,4,9);
   PRINT_ELEMENTS(coll,"coll: ");
   // replace all elements with value less than 5 with 0
   replace_if (coll.begin(), coll.end(),  // range
               bind2nd(less<int>(),5),    // criterion for replacement
               0);                        // new value
   PRINT_ELEMENTS(coll,"coll: ");

}</source>

coll: 2 3 4 5 6 7 4 5 6 7 8 9
coll: 0 0 0 5 6 7 0 5 6 7 8 9

Use replace() to replace elements in a vector

<source lang="cpp">#include <iostream>

1. include <vector>
2. include <algorithm>

using namespace std; template<class InIter> void show_range(const char *msg, InIter start, InIter end); int main() {

 vector<char> v;
 vector<char>::iterator itr, itr_end;
 for(int i=0; i<5; i++) {
   v.push_back("A"+i);
 }
 for(int i=0; i<5; i++) {
   v.push_back("A"+i);
 }
 show_range("Original contents of v:", v.begin(), v.end());
 
 // Replace B"s with X"s
 replace(v.begin(), v.end(), "B", "X");
 show_range("v after replacing B with X:", v.begin(), itr_end);
 return 0;

} template<class InIter> void show_range(const char *msg, InIter start, InIter end) {

 InIter itr;
 cout << msg << endl;
 for(itr = start; itr != end; ++itr){
   cout << *itr << endl;
 }

}</source>

Use std::replace to replace elements in vector by value

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

1. include <algorithm>
2. include <vector>
3. 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 > v1( a, a + 10 ); // copy of a
  cout << "Vector v1 before replacing all 10s:\n   ";
  std::copy( v1.begin(), v1.end(), output );
  // replace all 10s in v1 with 100
  std::replace( v1.begin(), v1.end(), 10, 100 );
  cout << "\nVector v1 after replacing 10s with 100s:\n   ";
  std::copy( v1.begin(), v1.end(), output );
  cout << endl;
  return 0;

}</source>

Vector v1 before replacing all 10s:
   10 2 10 4 16 6 14 8 12 10
Vector v1 after replacing 10s with 100s:
   100 2 100 4 16 6 14 8 12 100

Use the generic replace algorithm to replace all occurrences of R by S

<source lang="cpp">#include <iostream>

1. include <cassert>
2. include <algorithm>
3. include <vector>
4. include <string>

using namespace std; int main() {

 string s("FERRARI");
 vector<char> vector1(s.begin(), s.end());
 
 replace(vector1.begin(), vector1.end(), "R", "S");
 for(int i=0;i<vector1.size();i++){
    cout << vector1[i] << " ";
 }
 return 0;

}</source>

F E S S A S I

Using "std::replace" to replace value 5 by 8

<source lang="cpp">#include <iostream>

1. include <algorithm>
2. include <vector>

using namespace std; // The unary predicate used by replace_if to replace even numbers bool IsEven (const int & nNum){

   return ((nNum % 2) == 0);

} int main () {

   // Initialize a sample vector with 6 elements
   vector <int> v (6);
   // fill first 3 elements with value 8
   fill (v.begin (), v.begin () + 3, 8);
   // fill last 3 elements with value 5
   fill_n (v.begin () + 3, 3, 5);
   for (size_t nIndex = 0; nIndex < v.size (); ++ nIndex){
       cout << "Element [" << nIndex << "] = ";
       cout << v [nIndex] << endl;
   }
   cout << endl << "Using "std::replace" to replace value 5 by 8" << endl;
   replace (v.begin (), v.end (), 5, 8);
   for (size_t nIndex = 0; nIndex < v.size (); ++ nIndex){
       cout << "Element [" << nIndex << "] = ";
       cout << v [nIndex] << endl;
   }
   return 0;

}</source>