Print left rotation of array in O(n) time and O(1) space ❤️

Given an array of size n and multiple values around which we need to left rotate the array. How to quickly print multiple left rotations?

Examples :

Input : 
arr[] = {1, 3, 5, 7, 9}
k1 = 1
k2 = 3
k3 = 4
k4 = 6
Output : 
3 5 7 9 1
7 9 1 3 5
9 1 3 5 7
3 5 7 9 1
Input : 
arr[] = {1, 3, 5, 7, 9}
k1 = 14 
Output : 
9 1 3 5 7

We have discussed a solution in the below post.
Quickly find multiple left rotations of an array | Set 1

Method I: The solution discussed above requires extra space. In this post, an optimized solution is discussed that doesn’t require extra space.

Implementation:

C++

// C++ implementation of left rotation of
// an array K number of times
#include <bits/stdc++.h>
using namespace std;

// Function to leftRotate array multiple times
void leftRotate(int arr[], int n, int k)
{
    /* To get the starting point of rotated array */
    int mod = k % n;

    // Prints the rotated array from start position
    for (int i = 0; i < n; i++)
        cout << (arr[(mod + i) % n]) << " ";

    cout << "\n";
}

// Driver Code
int main()
{
    int arr[] = { 1, 3, 5, 7, 9 };
    int n = sizeof(arr) / sizeof(arr[0]);

    int k = 2;
  
      // Function Call
    leftRotate(arr, n, k);

    k = 3;
  
      // Function Call
    leftRotate(arr, n, k);

    k = 4;
  
      // Function Call
    leftRotate(arr, n, k);

    return 0;
}

C

#include <stdio.h>

// Function to leftRotate array multiple times
void leftRotate(int arr[], int n, int k)
{
    /* To get the starting point of rotated array */
    int mod = k % n;

    // Prints the rotated array from start position
    for (int i = 0; i < n; i++)
        printf("%d ", arr[(mod + i) % n]);

    printf("\n");
}

int main()
{
    int arr[] = { 1, 3, 5, 7, 9 };
    int n = sizeof(arr) / sizeof(arr[0]);

    int k = 2;

    // Function Call
    leftRotate(arr, n, k);

    k = 3;

    // Function Call
    leftRotate(arr, n, k);

    k = 4;

    // Function Call
    leftRotate(arr, n, k);

    return 0;
}

Java

// JAVA implementation of left rotation
// of an array K number of times
import java.util.*;
import java.lang.*;
import java.io.*;

class arr_rot {
    // Function to leftRotate array multiple
    // times
    static void leftRotate(int arr[], int n, int k)
    {
        /* To get the starting point of
        rotated array */
        int mod = k % n;

        // Prints the rotated array from
        // start position
        for (int i = 0; i < n; ++i)
            System.out.print(arr[(i + mod) % n] + " ");

        System.out.println();
    }

    // Driver code
    public static void main(String[] args)
    {
        int arr[] = { 1, 3, 5, 7, 9 };
        int n = arr.length;

        int k = 2;
      
          // Function Call
        leftRotate(arr, n, k);

        k = 3;
      
          // Function Call
        leftRotate(arr, n, k);

        k = 4;
      
          // Function Call
        leftRotate(arr, n, k);
    }
}

// This code is contributed by Sanjal

Python

# Python implementation of left rotation of
# an array K number of times

# Function to leftRotate array multiple times


def leftRotate(arr, n, k):

    # To get the starting point of rotated array
    mod = k % n
    s = ""

    # Prints the rotated array from start position
    for i in range(n):
        print str(arr[(mod + i) % n]),
    print
    return


# Driver code
arr = [1, 3, 5, 7, 9]
n = len(arr)
k = 2

# Function Call
leftRotate(arr, n, k)

k = 3

# Function Call
leftRotate(arr, n, k)

k = 4

# Function Call
leftRotate(arr, n, k)

# This code is contributed by Sachin Bisht

C#

// C# implementation of left
// rotation of an array K
// number of times
using System;

class GFG {

    // Function to leftRotate
    // array multiple times
    static void leftRotate(int[] arr, int n, int k)
    {
        // To get the starting
        // point of rotated array
        int mod = k % n;

        // Prints the rotated array
        // from start position
        for (int i = 0; i < n; ++i)
            Console.Write(arr[(i + mod) % n] + " ");

        Console.WriteLine();
    }

    // Driver Code
    static public void Main()
    {
        int[] arr = { 1, 3, 5, 7, 9 };
        int n = arr.Length;

        int k = 2;
      
          // Function Call
        leftRotate(arr, n, k);

        k = 3;
      
          // Function Call
        leftRotate(arr, n, k);

        k = 4;
      
          // Function Call
        leftRotate(arr, n, k);
    }
}

// This code is contributed by m_kit

Javascript

<script>
// JavaScript implementation of left rotation of
// an array K number of times

// Function to leftRotate array multiple times
function leftRotate(arr, n, k){
    /* To get the starting point of rotated array */
    let mod = k % n;

    // Prints the rotated array from start position
    for (let i = 0; i < n; i++)
        document.write((arr[(mod + i) % n]) + " ");

    document.write("\n");
}

// Driver Code
let arr = [ 1, 3, 5, 7, 9 ];
let n = arr.length;

let k = 2;
// Function Call
leftRotate(arr, n, k);
document.write("<br>");

k = 3;
// Function Call
leftRotate(arr, n, k);
document.write("<br>");

k = 4;
// Function Call
leftRotate(arr, n, k);

</script>

PHP

<?php
// PHP implementation of 
// left rotation of an
// array K number of times

// Function to leftRotate
// array multiple times
function leftRotate($arr, $n, $k)
{
    // To get the starting
    // point of rotated array
    $mod = $k % $n;

    // Prints the rotated array
    // from start position
    for ($i = 0; $i < $n; $i++)
        echo ($arr[($mod + 
                    $i) % $n]) , " ";

    echo "\n";
}

// Driver Code
$arr = array(1, 3, 5, 7, 9);
$n = sizeof($arr);

$k = 2;

// Function Call
leftRotate($arr, $n, $k);

$k = 3;

// Function Call
leftRotate($arr, $n, $k);

$k = 4;

// Function Call
leftRotate($arr, $n, $k);

// This code is contributed by m_kit
?>

Output

5 7 9 1 3 
7 9 1 3 5 
9 1 3 5 7

Time Complexity: O(N), as we are using a loop to traverse N times.
Auxiliary Space: O(1), as we are not using any extra space.

Method II: In the below implementation we will use Standard Template Library (STL) which will be making the solution more optimize and easy to Implement.

Implementation:

C++

// C++ Implementation For Print Left Rotation Of Any Array K
// Times

#include <bits/stdc++.h>
#include <iostream>
using namespace std;
// Function For The k Times Left Rotation
void leftRotate(int arr[], int k, int n)
{

    // Stl function rotates takes three parameters - the
    // beginning,the position by which it should be rotated
    // ,the end address of the array 
      // The below function will be rotating the array left     
    // in linear time (k%arraySize) times
    rotate(arr, arr + (k % n), arr + n);
    
      // Print the rotated array from start position
    for (int i = 0; i < n; i++)
        cout << arr[i] << " ";
    cout << "\n";
}
// Driver program
int main()
{
    int arr[] = { 1, 3, 5, 7, 9 };
    int n = sizeof(arr) / sizeof(arr[0]);
    int k = 2;
  
      // Function Call
    leftRotate(arr, k, n);


    return 0;
}

C

#include <stdio.h>

// Function For k Times Left Rotation
void leftRotate(int arr[], int k, int n)
{
    int i, temp;

    // Perform k left rotations
    for (i = 0; i < k; i++) {
        // Store the first element of the array
        temp = arr[0];

        // Shift all elements one position to the left
        for (int j = 0; j < n - 1; j++) {
            arr[j] = arr[j + 1];
        }

        // Place the first element at the end
        arr[n - 1] = temp;
    }

    // Print the rotated array
    for (i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

// Driver program
int main()
{
    int arr[] = { 1, 3, 5, 7, 9 };
    int n = sizeof(arr) / sizeof(arr[0]);
    int k = 2;

    // Function Call
    leftRotate(arr, k, n);

    return 0;
}

Java

// Java implementation for print left 
// rotation of any array K times
import java.io.*;
import java.util.*;

class GFG{
    
// Function for the k times left rotation
static void leftRotate(Integer arr[], int k,
                                      int n)
{
  
     // In Collection class rotate function 
     // takes two parameters - the name of 
     // array and the position by which it
     // should be rotated
     // The below function will be rotating
     // the array left  in linear time
     
     // Collections.rotate()rotate the
     // array from right hence n-k
    Collections.rotate(Arrays.asList(arr), n - k); 
    
    // Print the rotated array from start position
    for(int i = 0; i < n; i++)
        System.out.print(arr[i] + " ");
}

// Driver code
public static void main(String[] args) 
{
    Integer arr[] = { 1, 3, 5, 7, 9 };
    int n = arr.length;
    int k = 2; 
    
    // Function call
    leftRotate(arr, k, n);
}
}

// This code is contributed by chahattekwani71

Python

# Python3 implementation to print left 
# rotation of any array K times
from collections import deque 

# Function For The k Times Left Rotation
def leftRotate(arr, k, n):
    
    # The collections module has deque class 
    # which provides the rotate(), which is 
    # inbuilt function to allow rotation
    arr = deque(arr) 
    
    # using rotate() to left rotate by k 
    arr.rotate(-k) 
    arr = list(arr) 
    
    # Print the rotated array from
    # start position
    for i in range(n):
        print(arr[i], end = " ")

# Driver Code
if __name__ == '__main__':
      
    arr = [ 1, 3, 5, 7, 9 ]
    n = len(arr)
    k = 2
  
    # Function Call
    leftRotate(arr, k, n)

# This code is contributed by math_lover

C#

// C# program for the above approach
using System;

class GFG
{
    static void leftRotate(int[] arr, int d,
                           int n)
    {
        for (int i = 0; i < d; i++)
            leftRotatebyOne(arr, n);
    }
 
    static void leftRotatebyOne(int[] arr, int n)
    {
        int i, temp = arr[0];
        for (i = 0; i < n - 1; i++)
            arr[i] = arr[i + 1];
 
        arr[n - 1] = temp;
    }
 
    /* utility function to print an array */
    static void printArray(int[] arr, int size)
    {
        for (int i = 0; i < size; i++)
            Console.Write(arr[i] + " ");
    }

// Driver Code
public static void Main()
{
    int[] arr = { 1, 3, 5, 7, 9 };
    int n = arr.Length;
    int k = 2; 
    
    // Function call
    leftRotate(arr, k, n);
    printArray(arr, n);
}
}

// This code is contributed by avijitmondal1998.

Javascript

<script>
// Javascript program for the above approach
function leftRotate(arr, d, n)
{
    for (let i = 0; i < d; i++)
        leftRotatebyOne(arr, n);
}
 
function leftRotatebyOne(arr, n)
{
    let i, temp = arr[0];
    for (i = 0; i < n - 1; i++)
        arr[i] = arr[i + 1];
 
    arr[n - 1] = temp;
}
 
/* utility function to print an array */
function printArray(arr, size)
{
    for (let i = 0; i < size; i++)
        document.write(arr[i] + " ");
}

// Driver Code
let arr = [ 1, 3, 5, 7, 9 ];
let n = arr.length;
let k = 2; 
    
// Function call
leftRotate(arr, k, n);
printArray(arr, n);

// This code is contributed by Samim Hossain Mondal.
</script>

Output

5 7 9 1 3

Note: the array itself gets updated after the rotation.

Time Complexity: O(n)
Auxiliary Space: O(1), since no extra space has been taken.

Method III(Using Reversal):

To left rotate an array by “k” units we will perform 3 simple reversals-

Reverse the first “k” elements
Reverse the last “n-k” elements where n is the size of the array
Reverse the whole array

Code-

C++

// C++ Implementation For Print Left Rotation Of Any Array K
// Times

#include <bits/stdc++.h>
#include <iostream>
using namespace std;
// Function For The k Times Left Rotation
void leftRotate(int arr[], int k, int n)
{
      // if k>n , k%n will bring k back in range
     k = (k%n);

    reverse(arr,arr+k);
    reverse(arr+k,arr+n);
    reverse(arr,arr+n);
    
      // Print the rotated array from start position
    for (int i = 0; i < n; i++)
        cout << arr[i] << " ";
    cout << "\n";
}
// Driver program
int main()
{
    int arr[] = { 1, 3, 5, 7, 9 };
    int n = sizeof(arr) / sizeof(arr[0]);
    int k = 2;
  
      // Function Call
    leftRotate(arr, k, n);


    return 0;
}

C

#include <stdio.h>

// Function For k Times Left Rotation
void leftRotate(int arr[], int k, int n)
{
    // if k > n, k % n will bring k back in range
    k = (k % n);

    // Reverse the first part of the array (0 to k-1)
    for (int i = 0, j = k - 1; i < j; i++, j--) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

    // Reverse the second part of the array (k to n-1)
    for (int i = k, j = n - 1; i < j; i++, j--) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

    // Reverse the entire array
    for (int i = 0, j = n - 1; i < j; i++, j--) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

    // Print the rotated array
    for (int i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
}

// Driver program
int main()
{
    int arr[] = { 1, 3, 5, 7, 9 };
    int n = sizeof(arr) / sizeof(arr[0]);
    int k = 2;

    // Function Call
    leftRotate(arr, k, n);

    return 0;
}

Java

import java.util.*;

public class Main {

    // Function for k times left rotation
    public static void leftRotate(int[] arr, int k) 
    {
      // if k>arr.length,k%arr.length will bring k back to range
       k%=arr.length;
        // Reverse the first k elements
        reverseArray(arr, 0, k - 1);
      
        // Reverse the remaining n-k elements
        reverseArray(arr, k, arr.length - 1);
      
        // Reverse the entire array
        reverseArray(arr, 0, arr.length - 1);

        // Print the rotated array from start position
        String result = Arrays.toString(arr).replaceAll("\\[|\\]|,|\\s", " ");
        System.out.println(result);
    }

    // Helper function to reverse a section of an array from start to end (inclusive)
    public static void reverseArray(int[] arr, int start, int end) {
        while (start < end) {
            int temp = arr[start];
            arr[start] = arr[end];
            arr[end] = temp;
            start++;
            end--;
        }
    }

    // Driver code
    public static void main(String[] args) {
        int[] arr = {1, 3, 5, 7, 9};
        int k = 2;

        // Function Call
        leftRotate(arr, k);
    }
}

Python

# Function for k times left rotation
def leftRotate(arr, k):
    # if k>len(arr) , k%=len(arr) bring k back to range 
    k%len(arr)
    # Reverse the first k elements
    arr = reverseArray(arr, 0, k - 1)
    # Reverse the remaining n-k elements
    arr = reverseArray(arr, k, len(arr) - 1)
    # Reverse the entire array
    arr = reverseArray(arr, 0, len(arr) - 1)

    # Print the rotated array from start position
    print(" ".join(map(str,arr)))

# Helper function to reverse a section of an array from start to end (inclusive)
def reverseArray(arr, start, end):
    while start < end:
        temp = arr[start]
        arr[start] = arr[end]
        arr[end] = temp
        start += 1
        end -= 1
    return arr

# Driver code
arr = [1, 3, 5, 7, 9]
k = 2
  
# Function Call
leftRotate(arr, k)

C#

// C# Implementation For Print Left Rotation Of Any Array K
// Times
using System;
using System.Collections.Generic;

class Program 
{
  
    // Driver program
    static void Main(string[] args)
    {
        int[] arr = { 1, 3, 5, 7, 9 };
        int n = arr.Length;
        int k = 2;
        leftRotate(arr, k, n);
        Console.ReadKey();
    }

    // Function For The k Times Left Rotation
    static void leftRotate(int[] arr, int k, int n)
    {
        k%=n;
        Array.Reverse(arr, 0, k);
        Array.Reverse(arr, k, n - k);
        Array.Reverse(arr, 0, n);

        // Print the rotated array from start position
        for (int i = 0; i < n; i++)
            Console.Write(arr[i] + " ");
        Console.WriteLine();
    }
}
// This code is contributed by Tapesh(tapeshdua420)

Javascript

// Function for k times left rotation
function leftRotate(arr, k) {
    k%=arr.length
    // Reverse the first k elements
    arr = reverseArray(arr, 0, k - 1);
    // Reverse the remaining n-k elements
    arr = reverseArray(arr, k, arr.length - 1);
    // Reverse the entire array
    arr = reverseArray(arr, 0, arr.length - 1);

    // Print the rotated array from start position
    console.log(arr.join(" "));
}

// Helper function to reverse a section of an array from start to end (inclusive)
function reverseArray(arr, start, end) {
    while (start < end) {
        let temp = arr[start];
        arr[start] = arr[end];
        arr[end] = temp;
        start++;
        end--;
    }
    return arr;
}

// Driver code
let arr = [1, 3, 5, 7, 9 ];
let n = arr.length;
let k = 2;
  
// Function Call
leftRotate(arr, k, n);

Kotlin

fun leftRotate(arr: IntArray, k: Int, n: Int) {
    // If k > n, k % n will bring k back in range
    val rotation = k % n

    // Reverse the first part of the array (0 to rotation-1)
    for (i in 0 until rotation / 2) {
        val temp = arr[i]
        arr[i] = arr[rotation - i - 1]
        arr[rotation - i - 1] = temp
    }

    // Reverse the second part of the array (rotation to n-1)
    for (i in 0 until (n - rotation) / 2) {
        val temp = arr[rotation + i]
        arr[rotation + i] = arr[n - i - 1]
        arr[n - i - 1] = temp
    }

    // Reverse the entire array
    for (i in 0 until n / 2) {
        val temp = arr[i]
        arr[i] = arr[n - i - 1]
        arr[n - i - 1] = temp
    }

    // Print the rotated array
    for (i in arr) {
        print("$i ")
    }
    println()
}

fun main() {
    val arr = intArrayOf(1, 3, 5, 7, 9)
    val n = arr.size
    val k = 2

    // Function Call
    leftRotate(arr, k, n)
}
fun leftRotate(arr: IntArray, k: Int, n: Int) {
    // If k > n, k % n will bring k back in range
    val rotation = k % n

    // Reverse the first part of the array (0 to rotation-1)
    for (i in 0 until rotation / 2) {
        val temp = arr[i]
        arr[i] = arr[rotation - i - 1]
        arr[rotation - i - 1] = temp
    }

    // Reverse the second part of the array (rotation to n-1)
    for (i in 0 until (n - rotation) / 2) {
        val temp = arr[rotation + i]
        arr[rotation + i] = arr[n - i - 1]
        arr[n - i - 1] = temp
    }

    // Reverse the entire array
    for (i in 0 until n / 2) {
        val temp = arr[i]
        arr[i] = arr[n - i - 1]
        arr[n - i - 1] = temp
    }

    // Print the rotated array
    for (i in arr) {
        print("$i ")
    }
    println()
}

fun main() {
    val arr = intArrayOf(1, 3, 5, 7, 9)
    val n = arr.size
    val k = 2

    // Function Call
    leftRotate(arr, k, n)
}

Output

5 7 9 1 3

Note: the array itself gets updated after the rotation.

Time Complexity: O(n)
Auxiliary Space: O(1), since no extra space has been taken.

Print left rotation of array in O(n) time and O(1) space

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