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× C++ Standard Library C++ STL Library


The C++ algorithm::copy_backward function is used to copy all elements in the range [first, last) to the range terminating at result.

Please note that this function does not reverse the order of copied elements. To reverse the order of elements, algorithm::reverse_copy is used.

Syntax

template <class BidirectionalIterator1, class BidirectionalIterator2>
  BidirectionalIterator2 copy_backward (BidirectionalIterator1 first,
                                        BidirectionalIterator1 last,
                                        BidirectionalIterator2 result);

Parameters

first Specify initial position of the bidirectional iterator1. The range used is [first,last).
last Specify final position of the bidirectional iterator1. The range used is [first,last).
result Specify past-the-end position of the bidirectional iterator2 where the result to be stored.

Return Value

Returns an iterator pointing to the first element copied to the destination sequence.

Time Complexity

Linear i.e, Θ(n).

Example:

In the below example, the algorithm::copy_backward function is used to copy all elements of an array to a vector, terminating at end of the vector.

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
 
int main (){
  int arr[] = {10, 20, 30};
  vector<int> vec = {1, 1, 1, 1, 1};
  vector<int>::iterator it;

  //copy all elements from array to vector
  copy_backward(arr, arr+3, vec.end());

  cout<<"arr contains:";
  for(int i = 0; i < 3; ++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 20 30
vec contains: 1 1 10 20 30

❮ C++ - Algorithm