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std::rotate vs std::rotate_copy in C++ STL

Last Updated : 05 Aug, 2017
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  1. rotate in STL:It rotates the order of the elements in the range [first, last), in such a way that the element pointed by middle becomes the new first element, i, e, to the left. CPP 
    // Illustrating the use of rotate algorithm
#include <bits/stdc++.h>
using namespace std;

// Driver Program
int main()
{
    vector<int> arr;

    // set some values: 1 2 3 4 5 6
    // 7 8 9
    for (int i = 1; i < 10; ++i)        
        arr.push_back(i);

    // Use of rotate
    rotate(arr.begin(), arr.begin() + 3, arr.end());

    // prints the content:
    cout << "arr contains:";
    for (auto i = arr.begin(); i != arr.end(); i++)
        cout << ' ' << *i;
    cout << endl;

    return 0;
}
    Output: 
    arr contains: 4 5 6 7 8 9 1 2 3
  2. rotate_copy:It copies the elements in the range [first, last) to the range beginning at result, but rotates the order of the elements in such a way that the element pointed by middle becomes the first element in the resulting range, i.e, left rotate. CPP 
    // Illustrating the use of rotate_copy
#include <bits/stdc++.h>
using namespace std;

// Driver Program
int main()
{
    int arr[] = { 10, 20, 30, 40, 50, 60, 70 };    

    // Use of rotate_copy
    vector<int> gfg(7);
    rotate_copy(arr, arr + 3, arr + 7, gfg.begin());

    // prints the content:
    cout << "gfg contains:";
    for (auto i = gfg.begin(); i != gfg.end(); i++)
        cout << ' ' << *i;
    cout << endl;

    return 0;
}
    Output: 
    gfg contains: 40 50 60 70 10 20 30

S

Shambhavi Singh 1
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