Arrays: Left Rotation | Java HackerRank

Arrays: Left Rotation

A left rotation operation on an array shifts each of the array's elements  unit to the left. For example, if  left rotations are performed on array [1,2,3,4,5], then the array would become [3,4,5,1,2]. Note that the lowest index item moves to the highest index in a rotation. This is called a circular array.

Given an array a of n integers and a number, d, perform d left rotations on the array. Return the updated array to be printed as a single line of space-separated integers.

Function Description

Complete the function rotLeft in the editor below.

rotLeft has the following parameter(s):

• int a[n]: the array to rotate
• int d: the number of rotations

Returns

• int a'[n]: the rotated array

Input Format

The first line contains two space-separated integers n and d, the size of a and the number of left rotations.

The second line contains n space-separated integers, each an a[i].

Constraints

• 1 <= n <= 10⁵
• 1 <= d <= n
• 1 <= a[i] <= 10⁶

Sample Input

5 4

1 2 3 4 5

Sample Output

5 1 2 3 4

Explanation

When we perform d = 4 left rotations, the array undergoes the following sequence of changes:

[1,2,3,4,5] -> [2,3,4,5,1] -> [3,4,5,1,2] -> [4,5,1,2,3] -> [5,1,2,3,4]

Sample Output

5 4
1 2 3 4 5
5 1 2 3 4


...Program finished with exit code 0
Press ENTER to exit console.

Source Code

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {

    static int[] rotLeft(int[] a, int d, int n) {

        int i, j, k, b[] = new int[n], c[] = new int[n];

        for(i = d, j = 0, k = 0; j < n; j++){

            b[j] = a[j];

            if(j > d-1){
                a[k] = a[i];
                k++;
                i++;
            }
            else{
                c[j] = b[j];
            }
        }
        for(i = n-d, j = 0; i < n; i++, j++){
            
            a[i] = c[j];
        }
        
        return a;

    }

    private static final Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) throws IOException {
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        String[] nd = scanner.nextLine().split(" ");

        int n = Integer.parseInt(nd[0]);

        int d = Integer.parseInt(nd[1]);

        int[] a = new int[n];

        String[] aItems = scanner.nextLine().split(" ");
        scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

        for (int i = 0; i < n; i++) {
            int aItem = Integer.parseInt(aItems[i]);
            a[i] = aItem;
        }

        int[] result = rotLeft(a, d, n);

        for (int i = 0; i < result.length; i++) {
            bufferedWriter.write(String.valueOf(result[i]));

            if (i != result.length - 1) {
                bufferedWriter.write(" ");
            }
        }

        bufferedWriter.newLine();

        bufferedWriter.close();

        scanner.close();
    }
}

Sample Output

5 4
1 2 3 4 5
5 1 2 3 4


...Program finished with exit code 0
Press ENTER to exit console.