C++ <algorithm> - replace_copy() Function

The C++ algorithm::replace_copy function is used to copy all elements in the range [first, last) to the range starting at result, with all values equal to old_value replaced by new_value.

Syntax

template <class InputIterator, class OutputIterator, class T>
  OutputIterator replace_copy (InputIterator first, 
                               InputIterator last,
                               OutputIterator result,
                               const T& old_value, 
                               const T& new_value);

Parameters

`first`	Specify initial position of the input iterator. The range used is [first,last).
`last`	Specify final position of the input iterator. The range used is [first,last).
`result`	Specify initial position of the output iterator where the result to be stored.
`old_value`	Specify the value to be replaced.
`new_value`	Specify the value to replaced with.

Return Value

Returns an iterator pointing to the element that follows the last element replaced in result sequence.

Time Complexity

Linear i.e, Θ(n).

Example:

In the example below, the algorithm::replace_copy function is used to copy all elements of an array to a vector, with all elements equal to 5 replaced by 9.

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
 
int main (){
  int arr[] = {10, 5, 38, 5, 5, 78};
  vector<int> vec(6);
  vector<int>::iterator it;

  //copy elements from array to vector and 
  //replace all 5 with 9 in the vector vec
  replace_copy(arr, arr+6, vec.begin(), 5, 9);

  cout<<"arr contains:";
  for(int i = 0; i < 6; ++i)
    cout<<" "<<arr[i];

  cout<<"\nvec contains:";
  for(it = vec.begin(); it != vec.end(); ++it)
    cout<<" "<<*it;

  return 0;
}

The output of the above code will be:

arr contains: 10 5 38 5 5 78
vec contains: 10 9 38 9 9 78

❮ C++ <algorithm> Library