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Left rotation of an array using vectors in C++
  • Last Updated : 26 Oct, 2020

Given an array arr[] of integers and another integer D, the task is to perform D left rotations on the array and print the modified array.

Examples: 

Input: arr[] = {1, 2, 3, 4, 5, 6}, D = 2
Output: 3 4 5 6 1 2

Input: arr[] = {1, 2, 3, 4, 5, 6}, D = 12
Output: 1 2 3 4 5 6

Approach: Using vectors in C++, a rotation can be performed by removing the first element from the vector and then inserting it in the end of the same vector. Similarly, all the required rotations can be performed and then print the contents of the modified vector to get the required rotated array.

Below is the implementation of the above approach:

CPP

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// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to left rotate the array by d elements
// here we are passing vector by reference to avoid copying
// that just make our program slow
void rotate(vector<int>& vec, int d)
{
    // Base case
    if (d == 0)
        return;
 
    // Push first d elements from the beginning
    // to the end and remove those elements
    // from the beginning
    for (int i = 0; i < d; i++)
    {
        // adding first element at
        // the end of vector
        vec.push_back(vec[0]);
       
        // removing first element
        vec.erase(vec.begin());
    }
 
    // Print the rotated array
    for (int i = 0; i < vec.size(); i++)
    {
        cout << vec[i] << " ";
    }
}
 
// Driver code
int main()
{
    vector<int> vec = { 1, 2, 3, 4, 5, 6 };
    int n = vec.size();
    int d = 2;
 
    // Function call
    rotate(vec, d % n);
 
    return 0;
}

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Output

3 4 5 6 1 2 

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