ProDeveloperTutorial.com

Tutorials and Programming Solutions
Menu
  • Shell Scripting
  • System Design
  • Linux System Programming
  • 4g LTE
  • Coding questions
  • C
  • C++
  • DSA
  • GIT
  • 450 DSA Cracker
  • 5G NR
  • O-RAN

Given an array and a number n, rotate the array by n steps to its right solution in C++

prodevelopertutorial February 7, 2019
Example:
Array = {1, 2, 3, 4, 5 ,6, 7};
n = 4

Output:
[4, 5, 6, 7, 1, 2, 3]

Explanation:
rotate 1 steps to the right: [7, 1, 2, 3, 4, 5, 6]
rotate 2 steps to the right: [6, 7, 1, 2, 3, 4, 5]
rotate 3 steps to the right: [5, 6, 7, 1, 2, 3, 4]
rotate 4 steps to the right: [4, 5, 6, 7, 1, 2, 3]

This problem can be solved in 2 different ways.

 

Method 1: Take the copy of the array and rotate the elements.

In this solution we take a copy of the array then, we replace the items based on the formula “(i + k)%len”.

This will start from the position to be rotated. Then copy the elements from the copy array to the original array.

Test Case:

K = 4, hence the position will become

i = 0 k = 4 len = 7 (i + k)%len = 4

i = 1 k = 4 len = 7 (i + k)%len = 5

i = 2 k = 4 len = 7 (i + k)%len = 6

i = 3 k = 4 len = 7 (i + k)%len = 0

i = 4 k = 4 len = 7 (i + k)%len = 1

i = 5 k = 4 len = 7 (i + k)%len = 2

i = 6 k = 4 len = 7 (i + k)%len = 3

 

Method 2: By reversing the array 3 times.

Reverse 1: Reverse the whole array

Reverse 2: Reverse the elements from 0 to k.

Reverse 3: Reverse from k to n.

 

Solution in C++

#include<iostream>
#include<vector>

using namespace std;


vector<int> rotate_method_1(vector<int> array, int k) 
{
	int len = array.size();
    //take the copy of the array
    vector<int> array_copy(len);
    for (int i = 0; i < len; i++)
    {
        array_copy[i] = array[i];
    }
    
    // Rotate the elements.
    for (int i = 0; i < len; i++)
    {
        array[(i + k)%len] = array_copy[i];
    }
    return array;
}

vector<int> rotate_method_2(vector<int> array, int k) 
{
	int len = array.size();
 
	reverse(array.begin(), array.end()); 
	reverse(array.begin(), array.begin()+k%len); 
	reverse(array.begin()+k%len, array.begin()+len); 


	return array;
}

int main()
{

	std::vector<int> array = {1, 2, 3, 4, 5, 6, 7};
	int k = 4;

	cout<<"Before Rotation "<<endl;

    for (int i = 0; i < array.size(); i++)
    {
        cout <<array[i] << " ";
    }

	cout<<"\n\nAfter Rotation using method 1:"<<endl;

	vector<int> result = rotate_method_1(array, k);

    for (int i = 0; i < result.size(); i++)
    {
        cout <<result[i] << " ";
    }
    cout<<endl;

   	cout<<"\n\nAfter Rotation using method 2:"<<endl;

	result = rotate_method_2(array, k);

    for (int i = 0; i < result.size(); i++)
    {
        cout <<result[i] << " ";
    }
    cout<<endl;

	return 0;
}

 

Output:

Before Rotation

1 2 3 4 5 6 7

After Rotation using method 1:

4 5 6 7 1 2 3

After Rotation using method 2:

4 5 6 7 1 2 3

 

List Of Tutorials available in this website:

C Programming 20+ ChaptersC++ Programming 80+ Chapters
100+ Solved Coding QuestionsData Structures and Algorithms 85+ Chapters
System design 20+ ChaptersShell Scripting 12 Chapters
4g LTE 60+ ChaptersMost Frequently asked Coding questions
5G NR 50+ ChaptersLinux System Programming 20+ chapters
Share
Email
Tweet
Linkedin
Reddit
Stumble
Pinterest
Prev Article
Next Article

About The Author

prodevelopertutorial

Follow this blog to learn more about C, C++, Linux, Competitive Programming concepts, Data Structures.

ProDeveloperTutorial.com

Tutorials and Programming Solutions
Copyright © 2022 ProDeveloperTutorial.com